A couple of thoughts on shorediving the Big Island- One of the things that makes Kona side shore diving so good is the lack of rivers, streams, soil and relative lack of sand. Rain doesn't effect the diving in all but the craziest circumstances. I've flown into Maui and seen a red ring around the island, in Kona it can dump 2-3 inches of rain for two days straight (which is a rare event, generally the other islands or the Hilo side of the Big Island take the brunt of the rainfall much of the time) and you can go just about anywhere and step into 100' plus viz if surf isn't an issue. The relative lack of sand makes for the need for more discerning choices of entries and exits, but it often means zip/nada for a surface swim, you step off the rocks and you are on a reef. In either case, high surf can effect getting into the water when it comes to shore dives, in Kona it can go from impossible to fantastic overnight once the surf drops. Boat operators in either Kona or Maui usually should be able pick their sites to max out viz and water conditions when the shorediving's questionable.
If you're only here for a week, there's no real need to seek out "Aggressor" sites. Many them you won't be able to reach, a few of them you could reach (Thalassamania has talked about South Point on occasion, one can drive down to Manuka in an hour of offroad driving with a 4wd vehicle and such), but there's no real guarantee that just because the Aggressor goes there it's a "better" site... the coast is loaded with good sites, the day boats just don't go as far, the Aggressor doesn't even go north of the Kona airport and there's loads of great diving to the north. You'll be able to find lots of very good diving with a reasonable drive time .
Spoolin mentioned the turtles, they're definitely bigger on Maui, and if you've got non-divers in the group who's idea of a vacation is beach after beach, Maui offers more beaches with less travel times in that regard.