Excels give a lot more feed back & power.
When do you want a lot of power from fins? Assuming we're talking about recreational diving? When I'm in the water I barely move most of the time, and any of these Mares fins works really well. I do sometimes see divers out on a route march or maybe a race, but I don't join them. They always end their dives way before I do anyway.
IMO the most important characteristics of fins are comfort, durability, comfort, propulsion ability, efficiency, and did I mention comfort? And of course colour.
Note that "efficiency" is not the same as "effectiveness". If you really need a lot of propulsion, such as if you regularly have to fin against a strong current (I can think of land-based dives like that) then sheer brute force becomes important, whatever it costs you in effort and tiredness. Most of the time though "efficiency" is way more important - the ability to achieve an adequate speed with minimal effort.
In my experience any fin can also be used for backwards propulsion, such as when you're trying to photograph close to a coral wall in a current. But I find these "conventional" fins quite up to the job. Some people swear by Force Fins for that in particular; IMO they're good though a bit wide for my taste, but don't come close to justifying the price charged for them.
Note - this is for recreational diving. For technical diving propulsion ability becomes relatively more important, though comfort remains the single most important characteristic.
