Oster, Wahl, and Andis all make excellent clippers. My advice is to go with a pro model as they are more powerful and durable than one labeled for pet or home use. And buy from one of the online places like Pet Edge or KV Supply if you want to save money.
This is a re-post from a different forum entitled "Human vs. Dog Clippers?"
Most people will tell you that 'you get what you pay for' and that you should get an expensive set of clippers. That has not been my experience.
I have tried a few different techniques with our standard 70 lb bernedoodle. I really think that your needs will vary quite a lot depending on the type of coat your dog has. Our dog has a very thick coat of fine soft fur. I used to use scissors for her, but now I have converted to clippers for most of the job, and just use scissors for her face, and a little bit of cleanup.
I use a snap-on plastic comb (5/8 inch). Most people will say that this clipper is too lightweight and that a plastic comb will not do a good job - it will fall off, or it will get caught, the clippers will bog down or overheat, etc. This has not been my experience. I found it works fine. As long as the fur is fairly clean and *very* well-brushed, it works great. I keep on top of it by grooming her every 2 or 3 weeks rather than waiting for it to be a big job. She lies on her side and I do one side, and then then I roll her over and do the other side. She's cool with it.
As a matter of fact, I borrowed a pretty expensive set of clippers this past weekend to compare. It was much heavier and more powerful than mine, and had less vibration. I did not like how heavy it was, but the low vibration was a nice thing I guess. It had a #4 blade on it - so it should have been pretty similar to what I have been using. Thing is, a blade is fairly fine, whereas a snap-on comb is widespread. Long story short is that I could not use that expensive set - it was terrible - it was like trying to run through her coat with a very fine toothed comb. Impossible. A snap-on comb on my clippers was more like running a wide-toothed brush through her fur - it glides through. I just run it through a few times - against the grain - and it provides a pretty even and nice cut. Keeping the coat fairly short also seems to prevent mats, but when she does get some matting around her legs I work them out by hand or sort of pull them out.
Again, I think it really depends on the type of coat you are dealing with. If your dog's fur is coarse and thick, you might need to opt for a heavy duty solution. You also need to consider if you want to maintain a mid-length coat like I do, or if you want to sort of shave your dog down every few months like many poodle (and poodle cross) owners opt for.