Long story short Immersive College of Winterhold adds a lot to the college, ranging from quests, to spells, to new actives to AI changes, and is visually stunning. Obscure is more down to earth just makes some visual changes and adds a few notes. Overall if you're looking for a polished vanilla college with many small improvement go with Obscure. If you're looking for a mod that makes the college feel grand and epic and adds a lot to do in the College. Go with Immersive College of Winterhold.

For me a choice is obvious. Immersive is a one in a thousand mod. The quest is great, the visually are gorgeous , it makes the college really feel fresh. Yet somehow it isn't buggy or incompatible with everything. But a lot of people prefer Obscure, due to it feeling more down to earth and not making radical changes. Instead it focuses on small improvements that feel very vanilla.