Is it better to upgrade to an 64bit processor due to the technological advantages over an 32 bit processor or is it better just to stay with an 32bit processor due the the application compatability
With the AMD Athlon64 (or Opteron), you don't need to worry about application compatibility, since it runs 32 bit apps as well, with a performance bonus. Costs a bit more, but if thats not a problem, there's no reason not to get it.
Processors like the Itanium are not really suitable for home use, since they don't run many programs.
the amd must run either in 32 mode or in 64 bit mode, it cannot switch over and back between them without a reboot, the G5 can. get an AMD if u are going to run linux as u can get a fully configured 64-linux that runs the chip at full 64 capacity and really zips along, windows 64 is hopeless and has hardly any apps.