Dear Bryan and all!Please do not forget about some special hardware configurations such as Thin Clients.
For example we use about 50 machines as Fat LTSP clients with Intel Celeron and Intel Atom. Their RAM is limited to 2Gb by hardware. They use Ubuntu 16.04 LTS with MATE desktop environment.
Even if CPU is 64-bit compatible, it will be impermissible luxury (or high RAM usage in other words) of 64-bit OS. I prefer 32-bits here as it reduces RAM usage.
Please take into account my logic about 32-bit LTSP clients. And do not drop 32-bits completely.