One of my A4000 mobos has a soldered buster 11 chip. :-)
I find A4000 to be nicer as far as heavy upgrading goes, however A3000 can be put in Mirage 3000 case and be just as upgradeable as the A4000. There's something about the A4000 being the last big-box Amiga that makes it shine in my eyes better than the A3000 does, however this is only my personal view. When I look logically at features of both A3000 and A4000, I clearly see which has better and which has worse features in regards to certain aspects of design.
Socketed chips are useful nowadays, as any Amiga hardware is quite old, and if you are (un)lucky enough that only a custom chip fails, in case of a broken motherboard, you can easily replace if you Amiga is A3000. A4000 is a pain in the butt, with its soldered custom chips, but as long as you are careful and treat your A4000 motherboard well and with care, it shouldn't fail on you so easily. :-)
The best "value" for your money makes definitely an A1200 the winner of all, I think, as heavy expansion of it is the cheapest...and what you get in the end is pretty comparable to the best looking A3000 and A4000 setups out there.
