I would upgrade to Waldorf regardless of 32bit vs 64bit. Personal I install 32bit unless the hardware can handle more tha 4 GB RAM. Unless of course there is a 64bit program that you need to use.
As far as I noticed a 32bit program uses the FLAT memory model and the 64bit also.
I see that we can no longer simply "apt-get install ia32-libs" to gain 32bit application support under 13.10.