Yosharian
Arcane
Web is Transmutation and ain't nobody speccing into that. It is a useful spell though.And from level 3 onward you have vastly superior CC to Grease already. Glitterdust, Web and Pit being the 3 most note worthy ones. Also still works in most act 1 main story areas until you go to the Staglord's fortress.
Grease: Target has to save every round, if the succeed they still have to get up and take AoOs and can't take a full round action. Preventing full round actions for powerful melee characters gets huge the further you get in the game, and enemies basically have to save twice in a row to be able to get a full round action attacking you.
Glitterdust: Blindness gives 50% miss chance, -4 dex and str. Good, but not nearly as good as taking them out of the fight completely. Powerful enemies that would have huge AB and deal lots of damage per hit are still likely to fuck you up if they get past that miss chance. Furthermore the worst part is that it has a DC check every round and ends permanently on the first save the enemy makes. Main reason it's good though is that it targets Will saves which basically makes it a whole other class of debuff spell compared to Grease.
Web: Grapple condition still allows the enemy to attack at -2 even if they can't move. Only advantage is that the terrain is still difficult (=50% movement speed) even if they save.
Pit: Can't attack them while they are in it.
No way I'd consider any of these spells "vastly superior" to Grease. If anything Grease is vastly superior to them in the general combat environment. And in any case you should still be using all your level 1 slots at level 3 or 4. Are you going to rest 10 times in Tranquil River Bend fighting those Boggards with Web?
I mostly agree. One thing you're missing is that the Blind condition has significantly more impact. Can't attack or cast spells at distant targets. Be flat-footed = dead easy to hit, eat sneak attacks even without flanking (and even with Uncanny Dodge, I think).
What you're missing about Glitterdust is that it is a WILL SAVE. That makes it tremendously useful against enemies that are either immune to trip or have high reflex saves but low Will. Furthermore, Glitterdust doesn't carpet the battlefield with an AOE effect which can hinder you or your allies.
Glitterdust isn't strictly better than Grease but it has a lot of advantages and it is an excellent spell. You should be using it if you're specced into Conjuration.