amenities wise the bigger rooms have more space, bathrooms, beds...ocean views are generally better views (some non ocean view rooms can still see the ocean to some extent).
the bottom level rooms facing the pools can sometimes get mongoose running near/into them (really not a good thing)...but no reserved seating or anything like that. you can reserve cabanas or casabellas...or vip seats for the luau...but that can be done no matter what room you book.