Longer pads work better, IMO, as there is more surface area to come into contact with the rim. I recently bought some inexpensive Jagwire Mountain Sport 72mm pads and they were a definite improvement over the stock pads on my Tektro brakes.

My brakes squeal a little bit too, but over time it's gotten better. In the past I've adjusted my brake pads using two business cards and they still squealed. I don't bother any more.

If you want better stopping power in wet conditions get the salmon colored pads. I never ride in the rain so I just buy the cheap stuff and it works great.