Have stayed at both and at 3 more Orlando Embassy Suites including 9 days in May at the newest LBV South which was less than 4 miles away. I would go back to every one of them. We are a family of 5 "adults" and it works well for us, particularly the breakfast.
I find no difference in quality at all between the Doubletree and Embassy. Yes Doubletree is part of the DTD hotel group and walk-able but it is the farthest from DTD. They do offer a Continental or Hot Breakfast buffet. We got the continental and it was very good, and it was free via our reservation with a Mousesavers link. One thing to consider here is the parking fee.
Embassy LBV is maybe 5 minutes drive out and LBV South maybe 10 at most depending on the lights. I would go back to either but our stay at South was so nice this last trip I would probably choose it. It is by far nicer than the Doubletree and we could drive direct to parks via World Center Drive without having to go through DTD congestion.