As far as "defence"(in quotes because of topic, not because it is defense in 'Murican English) goes there is just so damn much to it aside from actual technique. Everything from threat assessment, to awareness, to strategic vs tactical vs application that I am not sure the "which style" question can get a great answer other than local availability of good training counts for a lot. I would rather sweat at a good traditional karate school than a terrible Reality Based Self Defense/Combatives school, even if the latter is a far better on paper answer to self defense.
As for body type, I think that is much more a small "s" style question rather than a big one. Tall, lanky fighters manage to exploit their assets and limit their deficiencies in damn near every type of fighting competition/style. Vitale K. would not have had success trying to ape Mike Tyson or Joe Frazier. In Kickboxing we have Hoost, Hunt, Sefo, and Schilt who all got it done with very different body shapes, but who competed in the same sport and trained pretty much the same Muy Thai/Dutch Kickboxing style. BJJ has lanky masters like the Brothers Nog, Bustamante, Werdum, etc. They also have Jacare and Palhares who are fucking tree trunks.
So the upshot is I think you can pick your pleasure/poison and then naturally gravitate to using the tactics and techniques that work best for your frame and abilities.