There are 4 main routes up Baldy (and variations). Most people do the Ski Hut route so I'll comment on that first.
It's not even close to the MWMT in terms of mileage. However, much of it is steeper than most, maybe all, of the MWMT. In addition, a lot of the Ski Hut trail is lose, nasty, unconsolidated stuff - hard slogging up and easy to fall on going down. The MWMT is good solid trail all the way. And, of course, Baldy tops out at 10,064 which is nothing like 14,500.
The Bear Flats trail from the village to the top of Baldy is longer, but still much shorter than the MWMT, it's steeper and harder than the Ski Hut trail, and, of course, it tops out at the same altitude.
In this area I think the circuit up San Gorgonio via Dollar Lake saddle and down via Mineshaft saddle is a better final practice hike for Whitney. It's actually a few more miles than the MWMT, all on good trail, and it has plenty of altitude gain. You still only get up to 11,500, though, so if possible you should plan to spend some time at or above 12,000 when you get to the Whitney area. 14,000+ is a factor all its own and it affects your ability to eat, breathe, and everything else.
Good luck, and have fun!
Last edited by burtw; 07/21/09 04:39 AM. Reason: changed subject line