1000% Seasonic is better. Thermaltake can't even come close to half the quality Seasonic produces. I would go with an Antec, XFX, Corsair unit WAY before a Thermaltake.
how about this psu? 750W XFX Pro Series XXX Edition (P1-750X-XXB9)
+3.3V - 25A, +5V - 25A, +12V1 - 62A, +12V2 - n/a, +12V3 - n/a, +12V4 - n/a, +5VSB - 3.0A, -12V - 0.5A
What n/a means? Is this psu single rail or multi rail?
How much xfx worse than seasonic?
They both have single +12V rail
#1: BUT: seasonic have +80 gold and xfx +80 bronze. Does +80 affect on quality/performance?
#2: Pros and cons of these PSU's (To each other)
80+ ratings are not to do with quality, just efficiency. Don't get confused and think a gold unit is going t be higher quality than a bronze unit. This is not always the case. A gold vs. a bronze unit will just make better use of the power from the wall and not be as had on your electricity bill. This difference will not be noticeable at all though.