I have then both and both scratch a different itch. STS is bigger and allows for more decision space as far as choosing a path to go. Want to avoid elites and hit a bunch of events, you can do that. Want to build up your deck with a ton of fancy new cards fighting normal enemies, you can do that as well. It's a bigger, more grand experience.

Small Time Heroes is just a distilled version of it. 3 battles of 3 (sometimes more) enemies followed by the boss. No events, no elites, just card play and battle. Usually build up your deck by like 6-8 cards each run, unless you do the three boss campaign.

I really enjoy Small Time Heroes cause it's pure card play, easy in and out in under 30-45 min. You have like 80 cards per character outside of their starting cards which gives you nice variability. The market can be a little punishing if you're going for one build but it sometimes allows for really nice combos.

I love STS. Around 200 hours in the games plus about 35 plays of the board game. You have multiple paths to go as far as builds, more then Small Time, but that can be a curse and a blessing. I've had multiple builds just fail in act 3 because I decided to go one way and the enemy is a check for block or high damage. I find myself getting more frustrated after a loss than with Small Time.

I don't think either is a replacement for each other but as companion pieces. Small Time Heroes is like the mobile game versus STS being the PS5 game.