I did buy a Bosch one a few years ago. It´s not as versatile (or fast) as one might wish, but there are tasks where no other tool will work as good. For examplöe sawing is quite slow, but opening a hole in a kitchen cupboard to route cables or plumbing in a confined space with teh cupboard standing close to the wall is a Job for those tools. Or removing teh stuff between tiles so you can take out just one damaged tile.
Oh, and they are loud and myke your hands numb.
AFAIK the Cordless Dremel one is a rebranded cordless Bosch oen, so you might want to check prices on both.
The current FEIn ones are very nice, although too expensive for a tool I use so sparingly.
In my case, having to change tools with a Hex key is no big problem. If i would use the tool day in day out, I´d go for the FEIN with teh tool-less exchange system.