Hi,

I was in the same situation as you about a couple of months ago,
choosing between the AmigaOne and the Pegasos. Some things that make
me take the leap:

* The A1 are talking about how could it would be to have a nice, 600
MHz G4 A1, because it would be passively cooled. I like silent
computers, but seriously degrading speed to get that...
* No new hardware is currently available... If you wait, they should
be a new 600 MHz A1 (the Ami'05) and the Vixxen accelerator card
(which in a future should also be able to run as a stand alone
computer).
* MOS hard is currently available and cheaper. There is even talk
about a new 1,7 GHz processor card.
* You find more native applications for MOS than for OS4 (even though
they are REALLY working hard to close the gap).

On the downside, it is true that the future of MOS is not 100% clear,
but there are lot of pleople out there that largely compensate for
that (coding / porting apps that should be part of the next release,
like a TCP/IP stack).