check out the parent site of the DIS and mousesavers.com That way you can look at Disney's pricing seasons, and various other discounts.
There are always trade-offs when looking at a trip to Orlando between what you pay, and what amenities you desire.
Like you could savea ton by eating pbj sandwiches in the room all week - but likely that's not a choice you want to make. Going back to the room to eat a meal can be a significant inconvenience. Eating a few breakfasts in the room, MAYBE worth doing.
Sometimes
free dining is not the best deal out there - or is comperable to other discounts. Often paired withhe value resorts it's one of the better discounts. However, there's a trade off. Disney offers free dining during one of the less desirable times of year. Free dining means paying full price forthe room portion, and full price for your park tickets. Christmas is the worst time of year to go price wise - so any other time is going to be better and likely crowd wise.
SO part of what I'm saying is that price is not the only consideration. When my family stays onsite, everyone can come and go as the y please via WDW's free internal transportation. If we stay offsite, then everyone has to go at teh same time - via rental car. When you stay offsite, you have to pay for acar, and parking - so that offsets some of the savings. OFten you gain a bigger room.
I've alos felt that groceries can be a bit of a toss up. It takes time to drive to a grocery store shop and get back to your hotel - that's time you could be ina park enjoying your vacation. It may not sound like a big deal, but it comes out to about three hours. When you are paying $20per waking hour or more to be at WDW - there's a tradeoff there. It may be one you consider worthy, or maybe not so much.
Another area of trip related expenses is the price of good footwear! A bad pair of shoes will ruin a vacation! Good shoes are VERY worth the money. We are veteran WDWer's - and DH made that mistake just two years ago. He insisted on wearing old shoes with worn treads to save the money. Our very first night, it was raining. He slipped, fell, hurt his ankle and got a large gash. It nearly ruined our whole week!
Another way to save money that many folks overlook is the length of your trip. You have to balance the cost of getting to WDW with the per day cost - but sometimes shortening your trip by a day makes sense. I've often shortened my trip by a day to stay at a better resort. I have also stayed at the value resorts, and sometimes offsite. I kind of like to mix it up!
So the answer to your query - I think - is going to be highly personal based on your preferences. You have the advantage of having been to WDW before.