bike Selection question for tomorrow.

I've got the third race in a four series event tomorrow.

These first three races are all indoor time trials on some great stations.  First one was flat, last one was rolling hills (had just podiumed the day before on an indoor tri so i was wiped) and tomorrow is a hill climb. 

Well, my tri bike is geared much higher than my roadie that I used to commute.  Last race was tough.....the lowest gears were hard on me but that could have been due to my exhuastion from the day before.

Do I use the tri bike - and have the data from using the same bike in four races that I will race with this summer, or do I save my legs and use my roadie which has three rings?

I'm really torn on this - I feel like I'm wussing out by using the road bike for the lighter gears and that I should be pushing myself with the tri bike.  I'm the only one in my age group so the competition factor doesn't really exist.

On the other hand...I feel like I should bring the tool that will allow me to do the job as easy as possible.

What say YOU?