[ QUOTE ]
Why not fly both?
[/ QUOTE ]
There's the best anwer yet.
I had time in a 152, 172 and PA28 before getting my PPL. If you don't mind an extra hour or few getting your license, the experience of flying different planes is a pretty good one. I'd recommend sticking with only one until after you solo and get into the x-c work, then get checked out and solo again in the other.
The difference between planes will get you in the habit of really using the checklists, rather than the just skimming or ignoring it because it is so familiar.
Also, check the schedule on all the planes for the last month or so and see which one(s) have more availibility. You'd think the Tommy would because there are three of them, but if no one is flying the 152 it might actually be easier to schedule. Looking at the past records will tell you pretty quickly.
Have fun!