In terms of products and quality? Corsair. Corsair power supplies are some of the best in the world - all of them are at least 80+ certified, and offer three to five year warranties - the Corsair HX1000W is probably the best, lol. Also, their only case the Obsidian 800D has got many positive reviews, and you can tell it looks solid. As well as their cases, Corsair RAM is also well known and trusted.
As for Thermaltake, their power supplies aren't exactly really trustworthy, and the AFAIK the majority are not 80+ ceritified. Their newer cases are OK, such as the Element series, although, for example with the Thermaltake V9, the fans die quite often, and their plastic locking mechanisms are quite flimsy. Their Thermaltake Level 10 case looks awesome IMO, but at a ridiculous price premium. As for CPU cooling, their coolers are OK. However, their watercooling parts/systems apparently suck big time.
However, Corsair tends to be more expensive than most brands, and Thermaltake the opposite, so, you get what you pay for, really.
Corsair is a better brand. Anyway, Thermaltake is selling very good PSUs: the Toughpower XT 775, the Toughpower XT CM 750W or the Toughpower CM 1200W are very good options. Take in mind that the manufacturer of those psu and the Corsair ones (HX and TX from 750W) is the same: CWT.