You will definitely want the maps for the Sierra if you are thinking of hiking through before late July. Remember that from Kennedy Meadows to Reds Meadow (more than 200 miles) you don’t cross a road. This isn’t the AT.
You might be able to get away with no-maps for parts of SoCal, although this probably isn’t the wisest of things to do in the desert. North of Sierra City the trail is pretty remote, but mostly followable. In 2003 the CCC had cleared section O very nicely and it might have been possible to get through without maps. Again, the remoteness of the land makes not carrying maps, or carrying minimal ones, difficult. Your best bet for not carrying maps would be Oregon and Washington, assuming that a wildfire or heavy rains don’t wipe out part of the trail and require you to hike around it. This hasn’t happened, ever, so I wouldn’t worrry much about that happening.
If you are comfortable not carrying maps, then don’t carry any. However, if you decide you do want maps, the ones in the guidebooks are exactly right. Otherwise, as Yogi said, the Harrison maps for the Sierra are the next best thing.
Suge