I switched to Advantage Multi last year after doing a lot of research -- including looking at the study on resistant strains. I think it's the best product in its class for our area. I'm in an area where HW is endemic, and where there are ivm-resistant strains documented: the Gulf Coast of the United States.
If I were not in an endemic area, and not in an area with documented ivm-resistance (i.e., where you are), I would still be using ivm-based products (Heartgard, Pet Trust, Triheart Plus, Iverheart -- all the same basic product). The reason is not only that it costs 1/3 what Multi costs, but you can use separate the flea prevention from the HW prevention if you want to. Ivermectin has also been used safely at this dose for decades (absent MDR 1 genes) and the doseage in these pills is very tiny. It's the most studied, most widely used HW prevention, and it works effectively for millions of dogs.
Unfortunately, ivermectin is no longer a great option for those of us in the Mississippi Delta, due to the resistance problem that's developing down here. You don't have resistant strains, and may never get them, as you are protected by a long, cold winter.