THPS is a lot more arcade-y in comparison, its easier to pick up and probably more fun when friends get together.
Skate uses the right and left analog sticks oppose to the D-pad + other button combo, it has a tougher learning curve, but its not unreasonable. It's truer to actually skating, so you can't string together crazy amounts of tricks but when you do something complicated its way more rewarding. You should definitely rent before you buy cause some people downright hate it.
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"Moris should be here soon to rub it in my face..." -Pizza
