I use Trifexis. Covers Fleas,Ticks, Heartworm and all parasites in one chewable per month.
Trifexis does not kill or repel ticks. I see this repeated quite often on here - if your vet is telling you this your vet is wrong.
Comfortis does not kill ticks either. It only controls fleas. Comfortis (spinosad) is the flea control that is used in Trifexis.
Bravecto and Nexguard both prevent fleas AND ticks.