I've been wondering exactly the same thing, and I'm also looking at the Tower 100 (black version). Keep us posted!
Scan UK sells both, and it seems like they're both PWM fans though. Other than the round/square pump, I can't see any difference.
Not sure if links are allowed, so just the descriptions:
Thermaltake TH120 ARGB Sync, 120mm All-In-One CPU Hydro Cooler w/ ARGB Lighting, 1x120mm PWM Fan
Thermaltake Water 3.0 ARGB, 120mm All-In-One CPU Hydro Cooler w/ ARGB Lighting, 1x120mm PWM Fan