Well what difference... apart from the classic Amiga machine will be much more expencive to catch a very lowend PC there's the nostalgic feeling pointed out already, and as you self said the PPC/OS4 bit also.
The best thing in my oppinion would not be to spend loads and loads of $ on a beefed up A4000 system that will still be old in comparrison to most anything. Instead get a cheapo A1200 with a 030 board and some memory, a lowend PC (0.5-1Ghz is well within the limits)... there will be plenty of meney left over that can go into an A1 with just a little more funding. That way you get the nostalgia of an Amiga classic, the power of a beefed system without draining all your savings, and you get to see the new road a head for the Amiga... it do take up a fair bit of space though.
