Hallo Hans!
> I want to buy a PDA (PocketPC) and of course it should be able to run
> squeak. Is there any model or any vendor which is better than others
> ? Is 64 MB RAM enough (some PDA has 128)... Should it be 400 Mhz
> (XScale, or is 200 MHz enough if no croquet running :-))) ?
As with most things relating to computers, more is usually better. That
is, higher CPU speed, more RAM, bigger screen, more features.  But the
top of the line isn't required.
64 MB of RAM should be enough for running pretty big images, including
the stock images.  Heck, I've run the stock images up until 3.4 with
only 32 MB of RAM, although with anything up to 128 MB of RAM a memory
card is reccomended.  One can get by with the SqueakVM and maybe only
one moderately sized image on a 64 MB PDA's internal RAM- and a couple
other non-squeak apps and other data- but any more and you'd need a
memory card.
PocketPCs split that amount of memory - 64 MB, etc- between "program
execution" (aka RAM) and "storage space" (aka disk space).  But, memory
cards are a lot cheaper than internal RAM MB-per-MB; I'd go with a 64
MB model and get a 256 MB SD card.
As far as CPU, Squeak and Morphic run "decently" at 200 MHz or higher.
Decent at the low end may be a little closer to slow though.  MVC is
fast on anything with a 50 MHz CPU or faster in my experience.  I would
reccomend getting a 400 MHz XScale PXA255 equipped PDA.  They can be
had for a decentp rice.
A bigger screen is super nice with Squeak.  Only one PocketPC device
has a bigger screen, and it's not even out quite yet, that being the
Tosgiba e805. And that one will be very expensive.
I would reccomend getting the Dell Axim X5 Advanced. 64 MB of RAM, 400
MHz XScale PXA255 CPU, built-in SD and CF slots, as well as the nicest
screen of that type (240x320 16 bit color) that I've ever seen.
USD$299 new through Dell's site. A very good price for a substantial
machine.
Just about everyone else where would say that one model or vendor is
the "best," but that really isn't the case.  If you are dead set on a
"PocketPC" (as opposed to most any PDA that could run Squeak) and have
a gigantic budget, I would wait until the Toshiba e805 comes out.
They're $599, for same CPU, 128 MB RAM, SD and CF slots, integrated wi-
fi and a 640x480 screen.