I have been researching this exhaustively.
You can get Revolution and Frontline Plus (be sure it's the Plus) online for significantly cheaper than from the vet, even including shipping (and, the vet will charge tax, typically online you don't pay tax).
Revolution works against heartworm, Frontline Plus does not. That's the major difference. Also, I have heard that if ticks are not your main concern, you can use both of them once every two months instead of monthly. They will just get somewhat less effective with ticks during the second month. But, I think vets always push things to the max. I do NOT give my cats distemper vacs every year. I don't buy that they need it that often, or that it does not cause other risks. Look what happened with rabies. Some say you need it yearly, some every three years. I recently asked my vet about the discrepancy, and he said that the shot is the same, it's the local laws that determine how often it's needed. I will NOT risk an injection site sarcoma because some jerk govermental idiot thinks I should give rabies yearly to indoor cats. Nope.
Of course, dogs are more at risk for both heartworm and rabies. My vet said even fleas are not much of a problem in MN, unless your pet comes directly into contact with another host animal. Fleas aren't just laying in the dirt up here, like they do in the south (or so I hear). I just try to keep in mind that what we are putting on our animals IS A PESTICIDE and DOES ABSORB into their skin. That is scary.
