My LMCE Core is AMD64, 1 MD AMD64, 1 MD AMD32. I run 32-bit on all.
Have 2 Fedora boxes (F9 & F8) AMD64 X2, AMD64 respectively both running 32 bit plus 1 Ubuntu box AMD64.
I tried Fedora, Ubuntu and LMCE as 64 bit but had issues on all 3 versions.
Right now, for me anyway, 32 bit seems the way to go - everything is happy.