Perhaps you could split your stay - first half at the Folly Field condo and remaining days at the DVC resort. With your stay being 10 months away, I would think you would have enough time to change the dates of your stay. If you're spending just a few days at the DVC resort, you could request a studio to cut down on costs.
Unfortunately, comparing a Folly Field condo rental and the DVC resort is not comparing apples to apples. We rent a condo each winter (2-3 months) about a mile from the DVC resort and frequent the DVC resort, use points to stay there at times, and friends/family stay there. Four of our grandkids have recently stayed at the DVC resort and absolutely love the resort, the CMs -the best, the pools, bike rentals, and all the activities. When two of our grandkids came down last winter, we never left the resort! We ate in our unit or at the quick service. They didn't want to waste time leaving property. I'm sure you will have a great time at Folly Field, but the activities and CMs are such a big draw to the resort. There are plenty of restaurants and Kroger near both locations. There is plenty to do outside either resort - dolphin/crabbing excursions, bike rentals, Discovery Coastal Center, mini golf (our kids prefer the one next to Carrabbas which is close to Folly Field), movie theater is nearby on a rainy day, discovering Pinckney Island, Bluffton, etc.
Whatever you decide will be a good choice as you will be enjoying the beauty of Hilton Head Island and all its amenities.
Jan