It depends on what your aim is.
If you want to just run old stuff that doesn't need much more than your basic A1200, then any A1 or pegasos is a huge waste of money for you. These machines are not designed with hardware compatibility with the original amiga in mind. Why would they?
To make a fairer comparison, let's take an A1200 with PPC card as a bare A1200 is not much use these days.
This A1200 can run most (but by no means all) classic amiga software. It is also capable of runing OS4 and MorphOS. Compatibility wise it is a good choice.
The A1s run OS4 and the Peg's run MorphOS. Both also run system friendly classic software, but by and large nothing that demands the original chipset, at least not without some form of emulation. However, emulating the older machine is still a valid way of getting compatibility so you can't really mark them down for that. In fact, as UAE proves, software emulation gives the broadest compatibility possible ;-)
The fact that you _need_ WHDload in order to run a lot of old games on your A1200 already weakens the argument that it is better for non system-friendly software/games. The A1200 needs software (WHDLoad client) to fix compatibility with game X, A1 also needs software (an emulator). Is it really that different in the end?
So it depends on what you want to do. If you want to run older software, the A1200 is more than enough. However, the fastest A1200 presently available is absolutely dwarfed in performance terms by the A1 and Peg, even when running 680x0 code, which of course, these machines have to emulate. If you want to run system friendly applications and games that just prove too much for the classic, then these machines suddenly seem a lot more attractive.
Of course, if you want fast 680x0 emulation there is also WinUAE, but unless UAE gets some sort of PPC emulation, software written for PUp/WOS/MOS/OS4 is not going to work on it.
