Well if it's a bragging contest, I've been using LiPo's for a year and a half exclusively and owned several different packs and brands. And the worst packs I've ever seen happen to be Trinity packs (their old 4500's)
I'm just messin around a little RB FIVE, so please don't take it personal. If the numbers on the packs are what they advertise, the 4900's @ 25C will actually be better packs than the 3800's @ 30C. But over a 5 to 10 minute run with a 1/10th scale car, I really doubt there will be any noticeable difference between this two high quality packs from top notch companies.
The brand on the pack really makes no difference unless the manufacturer isn't providing accurate ratings of their pack -- which is most likely the case with some manufacturers. If you want to get down to details, the only way to really know is to cycle a pack and pull numbers like we used to do with our NiMh packs. I have done this with several LiPo packs that I've owned and the CheckPoint 4900's (which are I believe they exact same packs as the TrakPower 4900's) are the best I've owned to date. Over a 6 min 35A discharge they have better voltage & lower internal resistance than my Orion's did and those are the numbers that you put down on the track for rip and top end, not the 'C' rating stamped on the case.
All in all, your not likely going to go wrong with any quality LiPo from any of the top tier manufacturers, be it Associated, MaxAmps, Orion, CheckPoint, TrackPower, Trinity (their new one's without the built-in cut-off), SMC, etc., as long as you compare their capabilities accurately. Personally, I'll take a higher capacity pack with a lower 'C' rating any time the constant amp draws are comparable because several things I've seen with lithium technology hint that it lasts longer when smaller percentages of it's capacity are used regularly.