Again, it doesn't affect game performance.
No matter how much the load times in HL2 suck, they still don't affect the performance once the level is loaded. And as far as load times are concerned, faster drives make the biggest difference as long as your fragmentation isn't extreme.
If you're having to hit the page file in-game, though, all bets are off.

If you're having to hit the page file in-game, though, all bets are off.