We've been spoiled by staying offsite in large, spacious, nicely appointed timeshare condos. We get more space (2 BRs, 2 baths, full-sized kitchen, LR/DR, balcony or porch) with more amenities (washer/dryer, double jacuzzi) for much less money than a single onsite Deluxe hotel room. From my sig below, you can see that we've stayed both onsite & offsite. For our family of 5 to stay onsite that we've had offsite, we'd have paid more than double to stay in DVC condos.
DVC condos onsite are lovely... and ridiculously overpriced. We sold our DVC timeshare while keeping our other, more reasonable timeshare points and trading into other nice places offsite. We relax more when we leave the hype and enticement$ of Disney resorts. We enjoy resort activities for at least a day or two of our vacations. My DH tops out on "Disney" otherwise. As long as the resort is located only a couple miles from the parks, it's still easy to drive back to our resort and relax midday.
We found the Disney transportation to be of mixed value. The gate drop-off at MK was most useful. We enjoy the boats & monorail, too, from Deluxe hotels. But we've had the "pleasure & convenience" of standing on our feet in long bus stop lines one too many times, so mostly drive regardless of where we stay. Driving between the 4 spread out Disney parks and our condos takes about the same time (or less) than waiting for & using Disney transport.
Other onsite benefits are easy to bypass as well. FastPass reduces the need for EE. Front gate package pick-up is almost as good as Disney resort gift shop package delivery (and available the last day of your stay, when we shop more). Hopper passes enable one to park-hop and you only pay for parking once a day. On days when we visit theme parks, we only swim a little while. On resort days, if we want poolslides, we visit a water park with the "plus" part of our hopper passes.
So the only real benefits (for us) to staying onsite are the interesting themes and the easy access to parks/restaurants from the Deluxe resorts, which are way-overpriced. When we've added a few hotel nights to an offsite timeshare condo week, we're reminded that our Disney hotel stays usually ended with us needing a vacation after our vacation. Separate sleeping rooms for us & the kids just works better for us. So does having a full kitchen for breakfasts & evening snacks. Having all that costs too much at Disney hotels.