I've done both, I love both...
so basically if we are not using our points we stay offsite. For our dollar we get more value offsite. Now we don't use Disney transportation nor do we do the DDP so those are not perks for us. We also are AP and AAA diamond members so we don't pay for parking, so the only true perk that we even use whether on or off site is EMH.
We stay onsite. We've tried off-site but it's not the same. Staying in The World is wonderful!
I would never consider staying offsite. I love the amenities and "magic" of staying onsite!