[Edi]

Hrmm, it could be. I need to check up on the ambidexterity mechanics when I get back home, but it certainly looks that way. My mistake.

I think the +1/+1 is a more elegant solution since it does not result in visible attack values that look overinflated compared to other base units in the game. I suppose it's a matter of preference. In any case, the Ulmish units should NOT get more than +1 to ambidexterity (for a total adex of 2) or it will piss on all sort of other thematics (such as assassins having good ambidexterity etc).