The only drawbacks I can think of are
1. that you can hurt your dog's feet if you touch the rotating drum to the nails for too long - it gets really hot really quick.
On average I do 2-second passes over each nail on one paw, going back and forth until all of them are short enough.
2. you'll have to work on getting your dog accustomed to the noise the Dremel makes.
I can't say enough good things about my Dremel. Quigley freaks out over regular nail clippers - there is no way I can use them on him without risking injury, and his nails are typical "terrier claws" that grow very quickly. If it weren't for the Dremel, I'd have a really hard time keeping them under control.