In my experience Dremel is low quality for high price. Some of their accessories are unusable flimsy plastic (e.g. the drill stand). Any no name will work at least the same if not better, and for only a fraction of the cost.
As about which brand is better, most consecrated ones (not Dremel) usually have two product lines: one for hobby use, the other for professional use.
The hobby ones are loaded with gimmicks, not very productive, and designed for the cheap. Usually made to last from tens of minutes to a couple of hours top (at an intense use). No replacement parts, no international service, no extended guarantee, and again: hobby tools are not meant for intensive use.
The professional ones are exactly the opposite: designed to be reliable and productive, to do one thing and do it well. The professional tools cost about 10 times or more than the hobby ones, so unless you drill holes all day long for your entire life, it only makes sense to rent a professional tool for occasional work, never to buy.
I have a Dremel that was about $200 and a no-name high speed rotary of $30. Dremel came with almost no accessories, only had a few bits. The no name one came with hundreds of bits.
In practice I'm using (and abusing) the no name tool, while the Dremel is sitting on a shelf gathering dust.