There’s various stuff (Inis, RftG, Mysterium, Celestia, etc) where I’ll always play with expansions (or at least the 1 expansion I have for RftG) as it doesn’t change the base game much, so “with or without expansions” isn’t a very varied choice.
Resistance: Avalon is definitely one where it could vary but I don’t. If people are new, I’ll start off with just evil + good, then a second round with the assassin and Merlin. But usually I do Merlin/Percival/Morgana/Assassin/everything else. I’ve never even played with the other roles.
Magic Maze - I’ve only played with the first few scenarios, despite also having Maximum Security. Mostly because the games I’ve played have always involved introducing it to new people.
Paperback + Hardback I generally just play with the basics and haven’t felt the need to complicate things further. Again, even though I specifically bought the Paperback expansion.
I have the fancy new version of Citadels with all the expansions. We tried one of the varied setups once and it slowed things to a crawl as everyone had to check their abilities multiple times per round. Though not as bad as playing Coup: Rebellion G54 at UKGE, where the varied setup destroyed your ability to bluff easily.
I’m quite glad the expansion costing as much (or often more) as the base game meant I held off. It led me to question how much I’d ever want to vary such a simple game and realising the answer was “not at all”.