Well, you'd be wrong on that point. A dremel is easier on your hands and wrists, but you'll go thru several cutting wheels (unless you buy the diamond wheel which isn't cheap) and have wheel dust all over the place. Dremel noobs may break a few wheels in the learning process with the potential of missing hunks of one's personal flesh. You also have volumes of metal filings too that have to be completely removed from your case with tack cloth or an oiled rag (followed by a cleaning with a degreaser so as to prevent shorts, etc...
Except for the shavings from the drilled hole(s), you have none of the mess or danger with a nibbler. The hunks of metal it cuts out are macro, so you can find them easily. The only danger is that you might develop some forearm and hand strength...
.bh.