it's not going to make a difference at all. a better ignition system is what "defines the need" for a better wire set. but for the hell of it, the wire with the least resistance is what you want. i had the 9mm frpp wire on my car for a while. they work just fine.
Bigger the Better I always think
Installed the 9mm set on mine recently.
Works great.
And the Blue dont look bad eather
I had to get a good set of dividers for them, the big wires flop all over other wise.
8's would work fine too if there is a cost difference. Depending how for down the road your upgrades will be, you may want to replace them by then anyway.
Plug wires are not intended to last the life of the car, but i know plenty of people who seem to think they are
The 10's might be over kill for most cars,
unless you plan a full race car with major ignition up grades.