I would definitely want Buster 11 so I could use a nice Zorro III GFX card. Anything else?
Do your homework before replacing the Buster for a Buster -11. Certain ZIII cards don't need it, some do, and some won't work even with it.
Spectrum - doesn't need Buster 11
A4091 - doesnt work in A3000 even with Buster 11