I've just started biking and was looking at 2 used models of trek, a 2005 model 1200 and a 2004 model 1500. 1500 is a year older and $150 more. Is it worth it, or just start with the 1200. Riding about 20 miles 3 times a week now on an old trail bike with road tires. Will be riding in a 90 mile fund raiser in Sept. I'm not looking to be fast, but I am competitive. Thanks