Heres a summary of my paintball and airsoft experience of the years.
I own two Airsoft guns, a P90, and a M4, both shooting around 380 FPS.
And own three painbull guns, shooting around 300 FPS.
We play Airsoft when there is a site we'd like to play with tight corners, i.e. in a building or warehouse. CQB is no fun with paintball, because it just hurts to damn much and can be very dangerous. While airsoft offers a sense of more realism due to the guns, style of play etc, but its just not as intense. Airsoft becomes much more strategic and played out with scenarios, i.e. hostages, bombs etc..
Paintball is purely for the shoot em up and make em feel it fun. I find paintball guns to be more accurate over 100 feet. And its easy to have Team Vs Team deathmatches, and play with folks that you don't know to well.
As far as the guns looking real in airsoft, is because thats how the airsofters like them... looking real. Its what makes the scenarios real.. the terrorist with a majority of AK47's and derivitives, and the assualting force, m4's, FNC's, Galil's etc..
Its for fun!