Hi ModellerCH
I had the battery Dremel for about three years, not really often used. I loved it, then it broke down. Repair was far too expensive, so I decided to change to Proxxon. I never had to regret.
Check out this shop: http://www.suter-meggen.ch/zubehoer/proxxon/index.htm, he has more than fair prices (also for kits btw:-)
I work with a Proxxon MM50 EF / 12 Volt (speed adjustable) and the NG2/E Trafo (also adjustable) with this you can use your tool on lower speeds for plastic and slightly higher speed for Resin.
From Proxxon you have a wide range of tools, nevertheless you can use the Dremel tools as well. I even use my Proxxon with drills >= 0.6 mm, I never destroyed one until now.
What Puente54 mentioned, the tool has to fit you. In my opinion the price should be second priority, you know the saying 'the one who buys cheap, buys twice'.
Maybe you go to a Coop Baucenter to compare, they have both brands, there you can compare which one meets your need, your hand and maybe your future add-on plans.
Hope i could help
Cheers Thomas