I'm not sure, but it seems like they buffed constitution (CON) significantly with regards to how much life you get. You get about 40 vitality per CON point now. I tried firing up the old game and it seems like you get less vitality given the same amount of CON.
Unfortunately this appears not to be the case (I just double checked). Constitution is giving the same amount of health in both D:OS and D:OS:EE.
Assuming things don't change at later levels, I suspect you're comparing two different difficulty settings. Keep in mind that "Tactical" took the place of the old "Hard" mode, and you get a -25% health penalty when playing on that mode (in both games). Normal mode (now "Classic") provides a +15% health boost (again, in both games). The "Easy" setting was renamed to "Explorer" (and gives an even larger boost).
I'm not sure what the formula for determining hitpoints is, but 6 con at level 1 = 62 health, and 5 con at level 1 = 52 (in both games, and before penalties or buffs from the difficulty setting).
