For me, solo really doesn't make a difference. I have been trying to stay at all deluxes and all mods, but go with what i feel is the best deal regardless if I am going solo or not. Some thoughts though on the ones I've stayed at:
Animal Kingdom--killer lobby, all the animals, and great restaurants--this is a very relaxing place; will be staying again this September.
Polynesian Resort and Villas--love the theme and tropical atmosphere, the walk to the GF, Monorail, small boat ride to other resorts and big boat ride to MK; didn't like the villas so much as the regular resort room and also the lobby can get quite busy with restaurants right off the lobby
Boardwalk Inn--like the theme better than other EPCOT resorts--more intimate feeling with smaller lobby area, walk to EPCOT and access to all the restaurants in World Showcase and walk to HS
Coronado Springs--room was okay, but loved the resort in general, especially at nighttime, and loved the food options--a lot of people complain about distances between things, but that's what I like--I'm a major walker and love this resort and all of the Disney parks for that reason
PO Riverside--loved my stay in the Bayou--loved the landscaping and the room, enjoyed the boat ride to Disney Springs; can't speak to the bus service because I had a car.
Beach Club--was my least favorite; theme didn't thrill me, liked the size of my room, but was definitely in need of repairs; the pool is definitely expansive, but very little shady spots to relax by the pool; like Boardwalk though, great access to EP and HS
Grand Floridian--theme is not my favorite, but the lobby is nice and airy and light; like the walk to Poly and access to Monorail and boats; staying for first time this coming September (2 nights attached to my 8 at AKL) so I'll have to let you know after I've actually stayed in a room
You can't go wrong with POR. I have no problem with the moderates, will be staying at POFQ in December and would have stayed at CBR this September had it not been for the construction.
Sorry for this long string of my opinions!