I live in Illinois (your neighbor state) and I use HeartGuard. My current dog was HW+ when he arrived in rescue and we fostered him through his post-treatment recovery period... yes, we wound up adopting him!
I have talked at length with vets about the various options out there and have decided to stick with HeartGuard. Of course, the stakes are higher with my dog because he was once HW+ and it is not recommended for dogs to undergo multiple treatments... it is very hard on them. My take-away from these discussions is that the vets think that HeartGuard is the best preventative out there.