I use a multi-speed and think it's safer--with plastic, it can start to melt and 'catch' or 'seize' in the plastic...and since different plastics melt at different temperatures, you can choose the right speed to ensure this doesn't happen.
And get 'Dremel" brand and wired for sure.
In terms of the accessories, I get mine at "Princess Auto" for a fraction the cost of the Dremel brand. Plus you can more strategically choose the tool for the job rather than have 'any tool for a job you'll never do'.
My 2 cents.
