For PPL, buy the cheapest flight computer you can get. They will all do the calculations required at the PPL level perfectly fine. Mine is the Jeppesen one made from cardboard and it's still serving me well four years after having gotten the license.
After your PPL, if you find you like (read: understand) the analog flight computer sufficiently well to keep on using it, and you use it regularly, you can always buy a metal one. But I also see a lot of pilots buy an electronic flight computer post-PPL, or use a flight computer that's integrated in their GPS, cellphone or PDA.
If you continue for a CPL/ATPL, well, by then you will know enough to make an informed choice between the four you mentioned.
Last edited by BackPacker; 17th Jul 2009 at 14:50.