Lower profiles will give better cornering traction if you are inclined to a bit of racing - other than a few minor things nothing much else - they give a harder ride as there is less rubber to absorb the shocks.
I personally dont see the point in alloy rims, and have never been inclined to get them even when someone near and dear was going to buy me a set for my birthday a few years ago. You can still put the tyres on appropiate size rims for leess money.
Alloys are expensive and more easily damaged than steel - the choice is yours.
If you want to be one of these boy racers that hasnt gone through puberty yet then they will be a must.