It depends on what you want them for...just trimming here and there or full clips etc. I bought some Liveryman Element clippers/trimmer when I had to take off my cobs feathers. They were great and really quiet for my boy who had never seen a pair before! They would easily do a clip if the coat wasn't too thick. They are meant to run for an hour on the cordless setting but they weren't showing any signs of dying when I was still clipping an hour later!
I love my 'Wahl Pro' clippers - they clipped winter coat off my my two youngsters with one charge. I was really pleased with them.
Wahl also do a cute little battery clipper called the 'Pocket Pro' great for fiddly things and ladt minute trim ups. I keep these in a travelling soap case, with its spare batteries, oil and blades. Well worth buying.
We have a set of Moser clippers. You can't hear them and they clip through anything! Last year I clipped out 2 Wooly mammoth cobs who's legs had never met a hosepipe and they just clipped straight through it all. They're very good for horses who dislike the heavy vibrations and noise of the larger heavy duty clippers. Would have them every time.