Currently my babies are on Heartguard and are doing well on it plus Max is more willing to take it than his previous heartworm medicine. Before he was on Heartguard he was on Sentinel and it worked good, the only thing is that I live in Texas and we have a flea population most year round. So even though Sentinel helps as a flea preventive from them reproducing won't prevent them from getting on your dog (the flea has to bite to become sterilize) it didn't help much. So I was giving my dog Sentinel and flea medication and was spending alot as Sentinel is not cheap. And the little boogger would not swallow the pill it was a hassle everytime he needed to take it. Since we switched to heartguard he's been doing good on it and eats it as its a treat type of thing as before I had to disguise the pill in peanut butter and give it to him with a biscuit. If he found the pill he would spill it out.
I know you didn't ask about Sentinel but Interceptor(which is made by the same company)is the same thing except Sentinel has that flea program but they use the same heartworm medicine.