The color of my white H2 is still the same and I doubt it will change over time. I have it for almost a year and no changes in color.
The H2 got dampening foam and the construction is more "closed", which makes it possibly more silent.
The H2 is also 2cm wider, but less deep and height. Which means it supports slightly higher CPU heatsinks. Not much of a difference, but still ...
The H2 has hot swap capable SATA HDD Dock and top mounted USB, headset, etc. ports. While the ports of the Lexa S are on the side and there's no hot swap Dock.
The Lexa S is possibly cooler, due to the side fan and 2 instead of just one top fan. Both cases can possibly contain water cooling.
The Lexa S has 2 separate fan controls for exhaust/intake. The H2 has one control for all fans.
The H2 has 2 detachable front fans with detachable dust filter. Allows for easy cleaning and/or changing of fans.
That being said I do have no issues with temps in my H2 at all. Especially not after adding a 140mm top fan. Which I mainly did to run the case fans at even lower speed to keep the cooling level. My idle/max temps are CPU 32°/47°, HDDs 31°/35°, NB 36°/54°, GPU 37°/77° (OC'ed).
I'd say the cases are pretty similar and it should be a matter of taste, I prefer the minimalism of the H2 and it's more silent build.