Your hispanic employees are smart guys -
I moved to long sleeves last year - other than the hottest days, having the sweat stay on the short cools you down more quickly. And the suntan is just vanity - it'll get yourself a nice carcinoma down the road. Long sleeves is where it's at.
To the original poster's question - this is just my opinion, based on my observations - The determining factor in a professional look to your employees is not so much the shirt (button-down, collared "bowling" shirt with "Joe" embroidered on the chest vs nice T-shirt w/ logo vs. polo with logo) as it is the pants.
Any of those shirts coupled with a ratty pair of jeans still looks ratty. Pair up any of those shirts with a nice pair of tan or green Dickie's, and you have yourself a nice uniform.
As Rick mentioned, keeping them clean is also important.
But to me, your preference of T-shirt/Bowling Shirt/Polo is just that - preference.
Again, my opinion, not based on any actual facts.
