I liked my C= A4000, I spent over £1000 in 3 months to upgrade it with Mirage tower, Scandoubler, Mediator, Voodoo 5, NIC, TV card, CyberStorm PPC/060, GVP SCSI card, etc and it absolutely flew. Way better than any of the PPC A1200's I had owned before. But of course my Pegasos is orders of magnitudes better and faster again (and, surprisingly, more "Amiga-compatible" than my Amiga was, as it runs more things with less hassle/reboots etc), so I'd have to say that this is my favourite "Amiga" model.
I also have a soft spot for the A600 though, as this was my first ever Amiga (I sold my SNES to buy one). If the A600 had AGA (or better) and a CPU slot like the A1200 it would have been perfect.