Varies a lot depending on the predominant forage species in the lakes you are fishing. In Maine where I am, rainbow smelt are the dominant bait in most lake trout waters I fish and are always a good choice for live bait.
If you are exclusively after bigger lake trout, then I think big dead bait may be the best bet on many lakes. I prefer to jig and catch nearly all my fish that way, but if I was really going for a trophy, I would get the biggest bait I could find, cut or stomp on it a bit to get the juices flowing, then drop it to the bottom and be prepared to put in a lot of time waiting. Not the most exciting way to fish, but big trout are fat, lazy, and cautious, so it’s tough to beat a supersized meal of the real thing served up fresh for them to swallow, no chasing required!