Actually, just a few years ago, the junior detailer (general dentists and junior grade officers deal with him) actually tried very hard to get one of those top spots or a location that's pretty close. Also, if you don't request a residency (remember, GPR and AEGDs are also residencies), you are likely sent to one of the major shore commands like San Diego or Norfolk. From what I hear, that's still somewhat true, but with the general dentist shortage, that "need" part has a lot more weight these days. I'll give you some real examples:
A buddy of mine's mind was set on getting stationed near LA, and wanted to do his AEGD at camp pendleton. Well, luck wasn't on his side and the Navy decided that year to shut that program down. Then, he was told the only other available AEGD was in Camp Lejeune since that command was seriously hurting for bodies.
Another friend I know wanted desperately get stationed in Japan...and guess what, he got it because it's actually a place most don't request.
The whole detailing process is so hard to predict though as the available billets vary from year to year. Just get your fingers crossed and get ready to pack and go anywhere. That's my advice.😉