Having a track day or 2, won't really hurt the box that much, if you are shifting correctly, and not over-doing it..

But when start banging the gears with the clutch being flung up and aggressive, gears and gearboxes don't like that too much (trust me, I know the hard way LOL), and to keep the oil in the box working just that bit longer while you are smashing it, I'd go the thicker..

but if the car is still relatively new, and all is in good shape and looked after, the OEM is more than fine.

I'm just a little podantic, and prefer going that little bit thicker.. especially for the 1st - 2nd gear shift.. it's always the hardest one anyone will do..