Thanks, Mike (@Esox) and Jim (@Chan Eil Whiskers), for your thoughtful comments. I like how we're all trying to figure out what works best, and that might vary from person to person. Guard span definitely matters, but so does blade angle, and we can't forget about blade exposure. I haven't even tried a TTO yet, let alone a SE, so you guys are ahead of me. I really appreciate your offer, Jim, to have the time to analyze your ATT SE1 and SE2. That would be cool. I've made a note about that in a file for future reference.
I find with guard span, like gap, that less is more. Not so much with blade exposure though.
Fatip OC heads offer generous blade exposure, but so do early Gillette TTO's. Both also have short guard span distances, but theres something about a TTO thats hard for me to quantify in use. They feel different than 3 piece razors and I dont understand why.
Given a rigid design geometry, combining generous blade exposure, minimal gap and a short guard span distance, you can shave very shallow very easily. The closer I can get the blades edge parallel to my skin, the smoother, more efficient and more comfortable the shave.