I use a Dremel ($39 variable speed, set at the LOWEST speed to manage heat and to take nails off very slowly - I use the drum tool for fine sanding) on my 6 mo pup. I started exposing her early just to the noise (first, I just held her paw and did nothing -- gave her a treat at the end) and now she is fine with it. We use extra care like one would/should with any tool -- e.g., my husband holds her paw when I operate the tool do it to keep tails, etc. out of the way. I go slowly which is why I use my husband's help.
What I have observed is that there is a tendency for people to get in a hurry and use the tool at too fast a speed. This generates heat in the nail and risks injury because of loss of control (taking too much of the nail off at the time). I do not use a Dremel on my two other dogs because they were not exposed to it as pups. If you go slowly and exercise normal caution, the Dremel is a very nice tool for nails. Basically, I use whatever tool my particular dog finds most comfortable. Nail cutting is not something that I enjoy doing and my dogs probably sense that. It might also be because my husband is helping -- he usually leaves dog things to me so it's a big deal when there is a "joint operation" in my house. In general he is squeamish about these things -- you should have heard him when I gave my dog an injection!! "Oh, I couldn't do that! I don't know how you can do this to our Hannah. Oh, that looks like it hurts!....and on and on...until I told him to please leave the room while I did it because it was the first time for me and I couldn't handle a husband that was freaking out -- my dog was perfect. Nancy Melone