Neither, I am staying with 1004 until they fix a few things. But if I had to make a choice, I would pick the 1005a, it has a lot of problems but a lot less than the beta.
I have heard there are problems with everything from USB to ATA100 and even SB Live.
Hopefully, the next bios will fix all of these things and maybe even decrease the CPU temp. My system is completely stable and I have no problems what so ever. The next bios would have to be really impressive and problem-free for me to take the risk of flashing a perfectly working system.