You will pay more in WDW than near WDW.
Not necessarily. I mean, you can save money staying offsite, and offsite you might get more hotel for the money, but there are plenty of $$$ offsite options, the Marriott JW comes to mind.
As to OP's question, When I visit, I often do a mix of offsite and onsite. With a short visit, a split stay probably doesn't make sense for you, but I almost always do splits.
Offsite, as noted above, you can often get more room for the money. One option Ilike is to spend 1 (arrival) night at one of the Flamingo Crossings hotels. I save $100+, sometimes several hundred, and there's a nice new Target over that way (pick up water/other drinks/produce/snacks) and some good quick serve places to eat. (Lime eatery is a favorite!) Just about all the hotels over that way are new and very clean. Several of the options also offer big suite rooms, and it can be really nice to have a big fridge, and we don't even cook!
But...they are not quite as fun as the WDW hotels, and not as convenient to the parks as some of the WDW deluxe hotels. You also need to think about transportation/parking fees. One thing I like about the WDW hotels are the fun pools. Most offsite places have boring pools.
At WDW, time is $. The extra half hour every morning that onsite guests get isn't huge, but it is something. The extra PM hours that the deluxe hotels get can be a fun plus if you will be at WDW on a Monday or Wednesday and can manage the late hours.
WDW's onsite food though has become pretty marginal. A big plus of some offsite time is being able to get better food at a lower price. For a while we used to always eat at WDW's TS, but they have really gone downhill. Last summer we ate at several WDW buffets and they were overpriced and mostly terrible quality. The buffets are now an absurd $60 per person!
WDW also lacks good produce. The fresh fruit options are very marginal. It is very hard to find a berry anywhere on property. Vegetables beyond mediocre salads are also hard to find. At most TS, the veggie is no more than a garnish. WDW is also big on covering everything with things like "cheddar spread," "spicy aioli," "zesty sauce", and ranch sauce. Reminds me of a school cafeteria trying to disguise mystery meat! blech! (those came directly off WDW's menus, btw)
Now it is worth adding that we usually stay onsite when visiting Universal, if visiting there is in your future. If you had asked about Universal's hotels, then absolutely they are worthwhile.