I got the 1TB fusion, and the extra space wouldn't make a difference. However, I'm not willing to pay for more than $0.99 Geekbench to run the 64bit test. Since I would only ever need to run it once, I'll let someone else do that.
The extra space I'm concerned about is the other 128 of SDD space. I understand that with the fusion drive, the SSD continually saves space for read/write/etc ... But I'm still nervous that a 3TB fusion drive might actually be SLOWER than what I have now (which is all apps on my 256 SSD and all data on my 2TB secondary internal)