I honestly liked the BG1 SCS challenges way better. BG2 SCS gets super dry toward the end of SoA because every mage uses the same goddamn set of contingencies/pre-buffs (Improved Invis/Mislead + SI:D + SI:A + PfMW + Spell Trap/Spell Shield/Spell Deflection/etc. + a ton of combat protections I don't care about because I need to get through to Breach PfMW anyway), so it feels like I'm just playing mage combats with a formula.
The tactical challenges in BG1 SCS were much more varied and interesting.