Install with 5400 and 7200 RPM Drives

Here is what I am planning on doing, I have 2 40 gig drives, 1 is 5400 RPM the other is 7200 RPM. I want to dual boot XP and 98. I want to partition the first drive and install the OS’s there and use the second drive to install any apps/games. Where sould I use the 7200 RPM drive? Will I benefit more from having the OS’s on the faster drive or the games/apps?