Invul is quite good enough for holding aggro, although one could always argument that ice is better. I have always used both invicibility and taunt for controlling aggro myself, dont think there has ever been problems in this sense.
Actually, invulnerable gets to be great for aggro control once you get invincibility which of course only becomes available after lvl 18. Before that with only taunt which is now capped, it is harder.
Ice is better for aggro control but has other penalties to it....
Fire / Fire FTW, sooooo much fun to play with and quite hard but well proud of my Fire / Fire 50 love him to bits.
DD
Ice is marginally better at aggro than Invun
(But both are good)
Invun will afford you superb protection vs smash / lethal. Ice is a bit more rounded, but probably slightly less tough than invun... partially because...
Ice and Invun share the property of becoming stronger the more mobs you face (Invincibility and Energy absorbtion respectively) although Invincibility gives more of a defence bonus.
Level 9 Power is considerably more useful in the Invun set, IMHO
Ice is slightly more offensive (has a AoE damage power, whereas Invun has scaling to hit bonus).
Ice stacks well with end draining (electric users or kinetics), or with debuffers (dark or rad).
So...
Not much in it. Both are solid, aggro grabbing tanks.
Ice slightly more offensive, slightly less defensive, slightly better aggro grabbing.
My advice is choose with concept.
However, if you know you will often team with a rad / dark user, go Ice
Can't go wrong with either, so I'd say pick something that would be more fun for you. Personally I would pick Ice, because it has a wider variety of interesting powers. Makes it more interesting to play for me.
Since Invince give such a good to hit bonus, I would call this rewarding to a more 'active' and 'punchvokery' style while Ice are a more 'passive' by having an aura that damages and slows down opponents for you.
Pick the one that suits your playstyle. Sticking some taunt enhancers in Invincibility doesn't hurt though.
UNION
Officer Cuffz lvl 50 Inv/Nrg Tank
Badge lvl 50 dwarf/human Peacebringer
Dark Air lvl 50 Ice/Cold Corruptor
Ayre lvl 50 Storm/Elec Defender
Total Cat: @Officer Cuffz
"When I say interview, I mean engage in combat and defeat..." -Laura Brunetti, on how to deal with Warriors.
To be honest, Ice and Invun play pretty similar (aside from what I said above), Whilst Stone is the toughest but weakest aggro grabber and Fire is most skwishy but most damaging.
The variety probably comes more from your secondary...
SS/ENergy - single target damage kings, good for solo.
Mace/Axe - middle of the road
Fire - AoE King. Excellent for big teams and more aggro.
Ice - Defence King. Will boost your toughness but least damage.
If you are interested much more in teaming than solo play you could also consider ice melee to go with either Inv. or Ice.
In my opinion the damage from ice melee is truly terrible (frost is okish, as has wide aoe cone). So makes soloing painfully slow.
However, it has ice patch which will help manage aggro in many missions, especially at lower lvls. It will also help you survive longer at lower lvls. Enemies cannot attack you or any of the team if they are slipping on ice, hence less aggro on the other players.
Sometimes if the group has aggroed 2 spawns you can drop ice to make some of the enemy slip. Leave them slipping on the ice while you move to the second spawn and gather the aggro there.
Both ice and inv. are good solid tanks, but ice patch often helps add alot to that. It doesn't help with AVs and I recommend taking unstoppable if you go the inv. tank route, it may allow you to tank the AV long enough for the team to defeat it.
Even in I7 I have tanked +6 council, as the only tank on a team, on my inv tank thanks to ice patch.
Paragon Girl
Ice, definitely.
You can make an absolutely awesome monster of a tank with ice/fire for pve purposes, i dont have one but they are great if you want to "wow" people especially if you add weave. Survivability and damage is great, ice/ is an outstanding set with anything and if anyone was new to tanking or the game ice/ would be my first choice on suggestion of what to try first for not only tanking from the crib but for great fun too.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
Thanks for the input everyone.
I'm still a little unsure, but I'll probably give ice a bash as it does look fun. Just that Hibernate looks a bit "meh" compared to unstoppable, and on paper at least, inv looks more powerful to me.
Thanks again for the excellent advice.
I find that Hibernate is a far more useful power than Unstoppable. However they are completely opposite types of powers.
Unstoppable gives you moments of Godhood, followed by almost certain death if you in a fight when it crashes ( some people are very adept at preventing this ) . Used well it is very fun, especially against enemies that have been giving you trouble.
Hibernate is a great power for saving your life. I find that I use it every 2 or 3 spawns, it allows you to constantly tank closer to your limit without fear. It is good at giving a feeling of relief when you are taking a pounding, also it is quite amusing seeing a really dangerous enemy beating on your indestructable shield. The animation is good too.
From experience Combustion from /Fire helps cover Invs lack of aggro generation early on. Also Ice/SS works well because Hibernate and the defence debuffs protection from Ice help deal with the Rage crash from SS really well whilst Rage really turns your Icicles into a good damage dealing power.
@Unthing ... Mostly on Union.
Ice is a very strong set... probably too strong if you ask me. It was thrown some good buffs due to the problems with defence... and these have remained even after the problems with defence have been sorted out in issue 7.
Invun is, as you say, slightly tougher and has a better level 9 power in unstoppable. However, Ice is more well rounded in its protection (probably tougher vs anything but smash/lethal/fire), has icicles for damage, and is the best aggro grabber in the business.
Whenever a team im on sees an ice tank, its smiles all around as we know we will be very safe.
[ QUOTE ]
Ice is a very strong set... probably too strong if you ask me. It was thrown some good buffs due to the problems with defence... and these have remained even after the problems with defence have been sorted out in issue 7.
[/ QUOTE ]It was thrown some slight buffs to compensate for the huge nerfs, nowdays it's more in line with others.
In line, yes... but a bit too "in line" if you ask me 
[ QUOTE ]
In line, yes... but a bit too "in line" if you ask me
[/ QUOTE ]
a bit too in line? does that even make sense....
In the same way that /regen scrappers are more "equal" than other scrappers
Thanks for the advice guys, I rolled an ice/ice tanker last night - yeah, I know I'm not going to be good dps, but I'm more aiming for team support anyway.
Had an utter blast with it, but I've not got much from Ice Melee yet, so time will tell about that.
lol i had brawl and frozen fists as my only 2 attacks for quite a while, icicles does pretty good damage though, ice patch is great from the ice secondary and adds to your survivability by a lot.
I'm purely PvE, aren't interested in Stone/xx as it just doesn't suit me and wish to avoid Fire/xx for the usual reasons and the fact my brute was fire/fire.
I tried an inv/ss a while back, and found actually holding aggro a chore at low levels, so I was looking at ice, maybe ice/fire.
How does ice/xx compare to inv/xx? Obviously aggro holding will be much better at low levels, but would inv/xx be a better choice overall, or is Invinciblity just not as good at holding aggro as ice (due to it's multiple dmg/effect auras)?
Thanks in advance for any advice.