Fenix-Store and 4sevens.com is the same thing: just different domains run by the same guy

As his business expanded, I think he decided it was smart to have a separate storefront because so many people were confusing The Fenix Store with the official Fenix company. For example, when the EX10/D10 came out, some people kept thinking it was a Fenix light.
That's only true if you are making apples/oranges comparisons between different battery chemistries. As the runtime/brightness charts in both selfbuilt and this_is_nascar's reviews show, a D10 with a li-ion (14500 cell) actually beats the EX10 with a li-ion (RCR123 cell) in both brightness and runtime.
If you are comparing lithium primaries, the D10 with a lithium (L91) still has a slightly longer runtime to 50%, although the regulation isn't quite as flat as the EX10 with a lithium primary (CR123).
Now, if you are comparing a EX10 with lithium chemistries to a D10 with NiMH or Alkaline chemistry... then it's a whole 'nother ballgame. But I don't think that's a fair comparison of the lights or their max potentials, it's just a comparison of battery chemistries.
Your comment that they have the same beam profile is true though: they share an identical reflector.
It's also perhaps worth noting that in addition to them being different sizes to accommodate their respective batteries, the EX10 has a SS bezel ring to make up for the reflector gap (since the EX10 is fatter, but using the slimmer D10 reflector). Whether someone likes this or not is just personal preference though.