Are any of the hotels close enough to any parks so as to get a huge benefit from the price differences? I mean, the Art of Animation resort looks good and is one of the more affordable but seems so far from the main bits of WDW. None are as close to a park at WDW as DLH is to DLP, but does that matter? Argh - too much choice!
As for closest hotels relative to the different parks:
Magic Kingdom: The Contemporary and The Grand Floridian (monorail, both very close. GF also offer a boat-ride, the Contemporary is about 5-10 minutes walk away).
The Polynesian is just a tiny bit further away, but it's still a short boat or monorail ride.
Note, these are the 3 most expensive resorts at WDW.
EPCOT: Yacht Club and Beach Club resorts are basically on top of the back door of EPCOT, a short walk or ride by boat away. Boardwalk Inn is slightly further away.
Hollywood Studios: None super close to the entrance, Swan & Dolphin are closest, but this is a 1-day park at most until the Star Wars area is done anyway. It's a bit anaemic if I'm honest, especially now.
Animal Kingdom: Animal Kingdom Lodge is a short bus ride away, it's outside walking distance, because the grounds of this resort are massive, thanks to the savannah area they have.
As for any of these being worth the increased cost over the added convenience... I'd say no.
The Contemporary is maybe the only exception, but it's an expensive place to stay for the convenience of being that close to MK.
The cheapest resorts are the furthest away from the parks in general, the moderates tend to be somewhere in between, though with the moderates you need to be wary of the size of the resorts themselves.
Coronado Springs and Caribbean Beach are both enormous, to the point that they have internal transportation.
And unless you're close to the main building you're looking at a long walk (or waiting for a bus) before you can get on a bus to a park in the morning.
The Deluxe Resorts are generally closer to one of the parks, but that does tend to mean it's a long way from another.
AKL may be an exception, though it is far from basically anything that's not Animal Kingdom, it has direct bus-lines to almost everywhere else, meaning that overall travel-time is shorter than average. Wilderness Lodge is quite similar, lots of direct bus rides to parks, with its only weaker connection being to EPCOT, which it shares with Fort Wilderness.