I just had a long conversation with my vet -- who is pretty thoughtful. We're in a heavy HW and flea area (Deep South).
I currently use Iverhart Plus (or Max) for HW currently because it's a generic form of the same active ingredients as Heartguard Plus -- and it costs about $28 per 6 pack at KV Supply online (free shipping when you order 2). I have not found a cheaper alternative online (though I've heard Walmart's Pet Trust form of Ivermectin, sold through their pharmacy, is even cheaper). I've also used Advantage for fleas for many years.
My vet thinks Advantage (and Frontline) may not be working as well as they used to, based on what he's seeing locally (they are 20-year-old products, with the active ingredients widely used in agriculture, so that makes some sense). He thinks Comfortis blows them away in terms of effectiveness for fleas. It ends up a little cheaper to give Trifexis (Comfortis + HW preventative) than to give Comfortis plus a separate HW pill.
However, his top recommendation for HW preventative is not Trifexis. It's Proheart, which is a shot given once every 6 months. The reason is compliance and convenience -- no one who is on it ever forgets to give the monthly pill, and the dog stays protected. I don't have that issue because we have a calendar alarm that goes off when all the dogs get the HW pill.