Pulsar can perma-mezzle minions with usual slotting(2acc/2disorient/2recharge). It really needs those two accuracy SOs though. It has a 50% chance of affecting LTs, which is handy in a big group. Very effective when soloing and still fairly useful on teams.
Solar Flare's description is a bit off there. It hits flying foes fine as long as they are within the range, but you DO have to be on the ground to use it. It does good damage but has 80% chance of a Knockback (not Knockdown/Knockup) so use it too often on a team and you'll find tankers and scrappers will get rather annoyed at you... is a handy attack chain filler when soloing though.
I'd pick Pulsar if you already have a workable attack chain, but Solar flare is by no means a bad attack. I'd aim to get both in the build eventually.
I probably will get both eventually, but I an short of enhancment slots at the moment (what PB isn't?!). I suspect that Pular would be a bit rubbish with only the one slot, where as Solar Flare might be useful. Havn't done a PB before though so I'm prepered to be told otehrwise.
I really should do something about this signature.
Pulsar won't be *really* useful until you can get it 6-slotted. It needs at least two accuracies in it to even be "momentary crowd control".
I think I ended up taking it pre-30 on my Human/Dwarf build the first time around and made slotting it a priority... it certainly made life in the early 30s go easier and allowed me to be a bit less fearful of groups of mezzing enemies.
I imagine Solar flare would work better if you just had the one slot to devote to it (no accuracy penalty) but it has a fairly long recharge and drains considerable endurance.
Go with your gut instinct! 
What do you want to be able to do? What is your style of play.
I ran a tank to 50 to get my PB so that answers the question for me, i play my PB to hit hard, i dont really care about leaving people stood there seeing birdies, i'd rather they were "arrested" to hell already.
Alternatively your play style may be more control + containment of the enemy while you take them down at your leisure. Your style, your choice.
Solar Flare though, even from when i had pretty much only just got it and given it a couple of slots was doing more damage than Gleaming Blast, and thats to every enemy within a very decent range. The knockback may annoy team mates but can be useful for getting minions off ur back while u try to quickly take down a Boss/Lt & with skill and timing you can always avoid [censored] the team off, i've even used SF to knock mobs that were straggling closer to the tank. or waited until a Controller had locked the mobs down and then unleased merry AoE hell.
With SF, Luminous Det and well slotted Photons you can have a lot of fun in tightly packed groups.
I'm running an all human PB at the moment, which is level 26, and I have to say that Pulsar looks to be an excellent power already.
Currently I only have it slotted with 2 Acc, 1 Disorient duration but it already has a profound effect on taking mobs down in a decent sized team.
Tactics are to follow the Tank in once Aggro is secured and hit Pulsar.
The mob capability to hurt you is reduced very significantly as most are staggering about for 15 seconds or so ... and in even that short time your team will be able to decimate the mob without taking anywhere near the normal amount of return damage.
It's already drawn a lot of favourable comments from other team members - particularly as the mob remains bunched up for any AoE specialists in the team and the Tank can still hold/regain Aggro when it wears off.
Speaking from experience as both a Scrapper and a Fire/Fire Blaster I would far rather have the mobs tightly bunched and disoriented than scattered all over the place.
As for Solar Flare I can't comment much, as I haven't tried it yet. Only thing I would say is that Solar Flare looks to be very effective in certain situations and for that reason I will take it later on in my build.
Pulsar on the other hand I feel can be used on just about every mob you come to and I'm concentrating on getting that slotted up first.
Hope that helps 
Proud member of FOXBASE ALPHA and coalition associates.
Hero 50's - 25
Villain 50's - 1
You manage to get a tank to team with?! A competant one? Most of the time my PB ends up doing the tanking. 
I took Solar Flare and I love it. It works on bosses (at least some bosses) and you get to gratuatously annoy teammates as well.
I really should do something about this signature.
I usually found myself tanking even WITH a competent tanker... 
Properly-built tankers are more survivable than a PB dwarfie, but most Fire tankers (the ones without "tough") and some Ice/Inv tankers will have poorer survivability. Of course if a tanker can just hold aggro then you should be able to mezzle or kill the mobs before they get too badly hurt.
I met very, very few tankers that could spot a cyst/void/quantum before I did though.
But it's not all bad: once you hit 38 you can "tankmage" in light form and really show up your teammates! 
Yeah, but your bind helps a lot with that!
I really should do something about this signature.
I can't claim authorship for that one but it's certainly been very useful!
Was playing my new scrapper yesterday evening and we got a cyst... The team must have included a kheldian earlier in the night. It spawned right at the back of one of the small side rooms in an indoor office map.
We just saw the Freakshow standing in the doorway, all view to the rest of the room was blocked. I had typed "Cyst!!!" in team chat as soon as I looked towards the doorway and pressed my target macro, but noone else realised it was there until it started spawning hordes upon hordes of unbound nicti...
"CYST dammit!!!!! - Fine then, I'll tank it."
Turns out that Spines/DA is very easy to solo a Cyst with.
Yay for double-damage auras, AoE heal and negative energy resistance!
Our tanker who hadn't noticed it was one-shotted by the BOOM.
I didn't stop laughing for 10 minutes...
I was thinking about how to utilise both Pulsar and Solar Flare effectively without causing my team to get really hacked off at me.
I should point out that I team a lot with SG only teams who won't be slow to let me know if I'm annoying them with SF
Anyway, to use both I think I'll start as normal and follow the Tank in and hit pulsar allowing the rest of the team a safer period of time and then as the mobs regain their senses I'll hit Solar Flare.
Hopefully by this time most will be 'arrested' with only a few to mop up.
Sounds good in theory and I can't wait to try it, once I get Solar Flare.
Proud member of FOXBASE ALPHA and coalition associates.
Hero 50's - 25
Villain 50's - 1
I've found that Solar flare can be used best on teams in the following situations:
+ To "tighten" a mob. If you go behind a mob you can often knock it towards the tank or a debuff patch.
+ When a controller AoE immobilise has been dropped- they usually negate knockback.
+ When there's a wall nearby or a handy corner that they can be knocked into.
+ If the tanker has trouble coping with a herd's damage, knockback can give them some breathing space.
+ When you're about to use Dawn Strike. Nothing says "BOOM!" like an PBAoE combo.
YMMV of course. And if you're tanking in dwarf form or there is no designated tanker... go wild!
I have a mostly human form PB, and am undecided whether to take pulsar or Solar Flare at level 26 (PvE only).
The way I see it: Pulsar: potentialy longer duration mez when slotted, but weak against bosses and lts without another stun to stack with it. Also inacurate.
Solar Flare: does damage, possibly more effective against lts, but slotting doesn't increase mez effectiveness, must be used on the ground, very weak against flying foes.
I really should do something about this signature.