#1. A 64 bit OS can run 32 bit applications so there is no need to downgrade from 64 to 32.
#2. A 32 bit OS is supposed to be able to address up to 4GB ram but its really like 3.2GB. You need a 64 bit OS to go higher then 3.2GB of RAM.
#3. There is no reason to use 32 unless your employer is forcing you to.
#4. If you somehow got a 32 bit Windows 8 you should stay with the 64 bit Windows 7 till you have a 64 bit Windows 8.