Other issues may arise may involve;
1. PPC's 32 general registers VS AMD's X86-64’s 16 general registers issues.
2. Pricing/power (i.e. bang for bucks) comparisons.
3. Running legacy software.
4. Availability.
5. ...
Binary abstractions techniques (e.g. virtual 68k processors, MS's dotNET, Tao's VP) may reduce CPU HW dependencies.