Pro 1.1 EFI vs FCP7 vs FCPX and BMD card

hello,

i just bought a used mac pro 1.1 Xeon 2.66ghz with 8GB ram and video card supplied by apple (geforce 7300). OSX Lion 10.7

I know it has EFI 32 bit that can be upgraded to 64bit.
I admit i still cannot understand what the 32b vs 64b boot can offer though.

I have also a PPC G5 2Ghz with FCP7, 10GB ram, BMD Decklink (2005 model) video card
with break-out cables and i installed the latest FCP7 supported for leopard via hack.

My questions are the following...

Using the EFI 32bit on...

Pro 1.1 EFI vs FCP7 vs FCPX and BMD card