It's a nice, easy, quiet walk from DTD to SSR, but you can also hop on one of the boats. If you look at this picture you will see SSR if you are standing in front of the Lego Store. This is an old picture and not taken with the best camera, but you can get the idea.
SSR is closer if you are walking but it also depends on where on the resort your unit is located. SSR is not my resort of choice but that is a personel opinion. OKW is only a 5 minute bus ride. The boat ride is so nice especially in the evening. I also like the bigger rooms at OKW. It is nice to be able to sit out on the balconey at OKW with a glass of wine. You can actually fit more than 2 people at a time on it. Good luck with your choice.
We stayed in Congress Park section of SSR in March. It was a very short walk to DTD. My DDs and I loved how convenient it was. There is a boat launch in SSR further down along with a boat launch in OKW.
When we were at Saratoga Springs we also stayed in Congress Park and had a great view of DTD from our balcony. It was wonderful to see the lights at night.