My bike came with a set of Schwalbe Smart Sams which are now worn and its approaching time to replace them. They seem a good all rounder. Most of my riding is XC on the South Downs, though will be tackling Mountain Mayhem next month. Question is, do I replace them with the same thing or try something different. Don’t want to break the bank so was thinking Conti Mountain Kings or Nobby Nics.
Any suggestions.

Smart Sams are passably fast rolling tyres with some half decent knobs for when you get offroad. I have it on the front of towpath commuter. The Smorgasbord is a cheapish goodish general offroad tyre. Might even be too much if you are riding hard packed chalky brideways

Or either of the two you mention would be fine