Ardent I see as a skinny High Roller. Lower tread, less grip but faster rolling. I run it on my hard tail for more XC-ish/trail duties. The Ardent does me okay in the winter also, just a little less power in the slop. I wouldn’t run it on the front though. Likely to slide, but seems okay on rear.
High Roller doesn’t drag too much and grips better. Just if you’re blasting around on smoother stuff the Ardent will still run faster. I’d run a HR on more trail to AM style riding. Or High Roller II… a lot more grip, but it is draggy. I run the HRII on my bouncy bike with a Minion up front, and really like it, though got fairly chunk 2.4/2.5 EXO tyres set up more for the Alps and might slim it down.
EXO if you’re doing flinty stuff. A little heavier though, but helps prevent sidewall slicing.
And yeah, the 2.35 HR is smaller than the 2.3 HR II.