I would think that Pirelli would last longer than your typical knobby, given that it's got more of them. Plus I bet it's quieter on the highway... is that what Tim's running on his KTM?
Maybe get one and put on your spare rim, then with somewhat minimal work you could do a side by side comparison? Would make for a fun Vail camping activity, perhaps...
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 89 TW200, 09 TTR125, 07 TTR90, 07 CRF50