Great post. I had to read it - can't view the vid at work - but I have to agree.
I own both an XD-s Mod.1 (waffle grips) 3.3 9mm...and an FDE Hellcat. Shooting they are very similar, but the ergos are quite different. The Hellcat grip is more "square" - thicker, but not as long front to back, compared to the XD-s, which is long front to back (especially with the #2 - larger - backstrap), but thin side to side. I have no problem per se with either one, and I have excellent grip on either one...but they definitely feel different.
Same goes for carrying - I carry IWB, both in Alien Gear holsters. Even with a full mag and one in the chamber, the Hellcat is LIGHTER than the XD-s. At least, it feels like it to me. I can also wear it higher in the belt than the XD-s without it being "too tall", due to its slightly reduced overall length, which makes it a bit more comfortable for me at work (I sit all day..grr...). But with only a 0.2" difference in thickness...neither one prints, and either one can be worn all day regardless of attire, weather, or activity levels.
The more I shoot the Hellcat, the more I get used to the slightly shorter sight radius...last weekend I was plinking at some steel in the yard, and at 10 yards I put 11 rounds into a 2.5" group so I think I'm doing fine. And it'll keep getting better, the more rounds I'm able to put through it. I'm not nearly as quick with the 'cat just yet...but it'll come with practice.
The biggest difference I've found is...I can load the XD-s by hand, quickly and with no problems, but I have to use the Uplula to load the Hellcat. Damn those springs are tough.
End result is...I am keeping both!