For all of you saying you're going offsite for future trips, how are you getting to the parks considering they charge to park there? Are you AP holders? Are you staying somewhere with a shuttle? Are you just going to pay that parking fee?
I would assume that a large portion of hotels offer shuttles.
I know when we went in 2011 we had a free shuttle to both WDW and USO but we did end up driving a few days due to convenience. Even then though let's say you drove 3 out of 5 days I would go to WDW (giving driving myself a leg up from the free shuttle) that's $66 in parking fees to WDW. But given that I'm in Orlando for 9+ days and let's assume I had free parking at the offsite hotel:
For a Value that means staying onsite would cost $117 (9 days)
For a Moderate that means staying onsite would cost $171 (9 days)
For a Deluxe that means staying onsite would cost $216 (9 days)
OR I could spend $66 for 3 days of parking at WDW
OR to assume worse that the free shuttle I chose not to take period at all for any of the 5 days that means I paid $110 for parking which is a difference of $7 for Value, $61 for Moderate and $106.
I'm also going to for comparison sake assume that I more than likely got a lower hotel nightly rate though all things should be tit for tat so if that offsite place had resort fees, etc. For comparison sake you may say that maybe you paid more per night at an offsite hotel but you got bigger space, etc OR it could be that you could get 2 rooms more reasonably offsite rather than cramming into 1 room at WDW.
A lot rides on how many days you would be staying onsite at WDW and how many days you would feasibly be paying for parking if you opted not to take a shuttle.
If you only stayed 3 days onsite for a value that's $39 in parking fees at a Value resort, $57 at a Moderate resort and $72 at a Deluxe resort vs paying $66 for 3 days of theme park parking.
In pure financial sense the ratio of overnight resort parking versus paying for theme park parking will depend on where you stay and how long you stay for and how many days you will be going to the theme parks.
*ETA: You'd also have to add up how many days you drove to USO if you went there as well.