rad, optimse that -res
**Acceptable "support" responses**
Its your fault
Its your computers fault
Its your ISPs fault
Cold. Optimise that -res. 
Seriously, I think it´s down to personal taste. Both secondaries offer nice synergetic effects. So, it's up to you if you'd rather work with anchors that are so damn useful but can be quite taxing on your endurance at times or if you would rather buff shields now and then and carry (among other very useful things) one of the greatest buffs a brute can get. (Frostwork is awesome, especially against AVs, Hamidon and similarly nasty things.)
In any case your sonic/* corruptor will be an asset to a team. I guess I would go for sonic/cold since I find it easier to think of a concept for that kind of toon. (Something like a banshee bringing the chilling cold of the underworld to the world of the living blablabla... 
)
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
Also depends on what kind of PvP you're looking for.
Rad for duels and such, Cold for teams and zones imo.
Both are awesome I'm pretty sure I'm making one of each.
thePhilosopher Martial Arts/Regen/Fire Scrapper
theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor
I'm also thinking I might make one of each, they are both too good to choose just one!
My MA IDs:
Fiend Space: 211464
if you want a cold run an ice/cold, running a sonic the autohit -res of rad is far better than the -res of cold which are tricky to plant with sleet (but it is uber) and you never really know if your -res portion of heat loss actually hits, an its on a huge recharge.
Theres a reason why rad/sonic defenders pwn, the sets synergise well, sonic/rad corrs are not as good but still damn tasty.
**Acceptable "support" responses**
Its your fault
Its your computers fault
Its your ISPs fault
sonic/rad corrupters are great imho. Over double xp weekend my sg sonic/rad team went from 1 to 40 and the debuffing was amazing. We fought back alley brawler 6 times in a row and with all the rad effects on him he went down so easily!
Stealth edit, in response to the stealth edit by previous poster:
This is what he really said, even if he changed the wording, later-on:[ QUOTE ]
We did back alley brawler 6 times in a row
[/ QUOTE ]
There are some things that sound so wrong, no matter how many times you hear them.
But yeah, a big team of all rads is awesome, we had an SG summerteam of rad/rad corrs last year, and it was silly fun.
[b][color=blue]Coldest War /[color=red]/ Omega Patient[/b]
[url="http://www.the-cow.net/"][color=red]The CoW Network (Blog) /[/url][url="http://www.collegeofwar.com/"][color=blue]/ College of War[/url]
[ QUOTE ]
[ QUOTE ]
We did back alley brawler 6 times in a row
[/ QUOTE ]
There are some things that sound so wrong, no matter how many times you hear them.
[/ QUOTE ]
How do you think he got the soubriquet Back Alley Brawler dude?
Synaesthetix:if your mum wasn't already dead I would go kill her for bringing
you into the world
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
We did back alley brawler 6 times in a row
[/ QUOTE ]
There are some things that sound so wrong, no matter how many times you hear them.
[/ QUOTE ]
How do you think he got the soubriquet Back Alley Brawler dude?
[/ QUOTE ]
after spending a night out with KS...
Which one?
sonic/cold corruptor? Or sonic/rad?
My MA IDs:
Fiend Space: 211464