Look at quests as well. Both races can do the monk quests from Cabilis and Freep/Qeynos, but I think it is easier for the Iksar to do the Human quests than vice-versa.
If you want to be (more or less) unique, be a female Iksar monk. I've only ever seen ONE. I know not as 'attractive' looking as the human counterpart (well maybe it is to other ikkys).
I have a (male) Iksar monk, who has done the shackle quests up to Steel and the Purple Headband/Red Sash quests. I enjoyed doing all, some I've done several times. Also no one mentioned lack of night vision for humans. As far as the xp penalty, you may not even notice, I sure haven't, cause you will be having fun in the front line.
The other thing about a monk is the AC weight penalty. AC goes down if you carry more than a certain amount based on level. Just an added wrinkle but then again we get FD, Mend, Sneak, Safe Fall, Intimidation, Disciplines....