I would say Traps.
Full positional Cap debuffs. Known to kill AVs / GMs.. More then enough builds out here that you can port over to any AT with minor changes.
Overall all my Traps toons Defender, Corruptor and Mastermind all have the same sets slotted, along with similar power pool slotting. What is different is the attack powers which need to be slotted accordingly to fix the shortages in defenses from one build to another.
1. Why Soft Cap is Important : http://dechskaison.blogspot.com/2011...important.html
2. Limits: http://paragonwiki.com/wiki/Limits
3. Attack Mechanics: http://wiki.cohtitan.com/wiki/Attack_Mechanics
4. Rule of Five: http://wiki.cohtitan.com/wiki/Rule_o...e_Law_of_Fives
Cold/Sonic
Benumb: -62.5% damage, -865%regen
Infridgidate: base effects -31.3%defense, -37.5%damage, -87.5%recharge, -87.5%movement speed.
Heat Loss: -300%recharge, -30%resistance, -30%movement speed
Then add the -20% resistance for all sonic attacks..........
A cold/Sonic is a debuff machine, I think one of the best.
OLD SCHOOL PvP
Rad/Psi,Psi/Em,Fire/Em,Cld/Sonic,FF/Sonic,Grav/Ta,Storm/Psi,Sp/WP,Fire/Psi,Sonic/Pain
RIP:Southern Comfort PvP,PE PvP,INTEGRITY PvP,After School Special PvP Test SG's,TPvPL Season1+2 Runner ups
For pure AV killing, /sonic wins.
You want a Traps/Sonic.
When there is no room left in Hell, the Dead shall walk the earth.
The -Dmg for Infrigidate is for Fire damage only, it does not affect other damage types.
Honestly I say flip a coin and go with it. You wanted pros/cons here a quickie list:
Cold/Sonic
Pros:
-Res machine, especially with HL.
Def buff (at least the shields) work on teammates regardless of your location
Benumb is a rare power that does much to minimize the danger of an AV
Artic Fog provides resists to slow and -rch for teammates within range, very nice.
Cons
Needs a high recharge build to make Benumb perma, or even close to perma
Benumb just might miss
Sonic's only practical aoe is a cone. Not really a terrible con, but it has to be considered.
Traps/Dark
Pros
With FFG + Maneuvers + 2 Dark aoes you are effectively soft-capping the team against even cons. The -tohit from Dark, of course, will decrease against higher cons and ranks.
You get a heal from /Dark, which can come in handy since Traps doesn't have one.
Partial mez protection from FFG
Tenebrous Tentacles works well with Traps since it keeps foes within the debuffs and Caltrops (reduces scatter)
Dark Pit + Seekers can stack stuns. I'd consider it a bonus when it happens rather than depending on Seeker's chance to stun.
Easy to soft-cap with FFG
Cons
/Dark won't be as effective as /Sonic against the AVs and GM you (OP) are hoping to hunt
FFG will trail behind you and can act wonky in caves. This means you can be more suscepible to mezzes than you may expect.
Teammates will not get your buffs if they are out of range or out of LOS.
Since I called Howl a "con" for being a cone I should do the same for Dark's aoes, since they're cones too.
So, if the objective truly is big-game hunting, I'd flip a coin for the primary and choose /sonic for blast set. As for general pve teaming, whatevah.
Global = Hedgefund (or some derivation thereof)
I enjoy traps because of the versatility. The gadgets are neat, and your style is going to change whether you're soloing, TFing, or in a trial. Heck, I've been in Hami Raids where my sole job was 'keep the Hami tanker in range of regen.' The only truly waste of a power in Traps is Time Bomb, which has needed reworked since it was introduced, but doesn't seem like it'll ever get it.
One thing I'd say Traps has going for it in solo play is that the FFG gives you some status resistance. I'm not too familiar with Cold, but I think that's something it lacks.
traps/sonic
or
cold/sonic.
Both really fun builds! 
The sleep in Sonic really makes setting up you traps trival. You don't NEED the sleep to be effective but it helps in various situations.
When there is no room left in Hell, the Dead shall walk the earth.
Cold domination. Make yourself perma haste while you're at it
Kill the enemy. Take their souls. Drink their blood.
Hey all,
I've been meaning to make a debuff heavy defender since I got back into the game to help melt down AVs in trials, as well as for general content and all round good times. Both of these set ups sound pretty fun, traps/dark as a proc machine and all the good things traps does, and cold/son as a mighty -res caster.
Any particular pros and cons to either? It'd be nice to be able to solo or hunt GMs or other distractions like that as well with whichever one I build, it its not a necessary requirement.
Here you come with a stupid name like Fixer - brutalkillz_