Hey! Looking into my first bike purchase! Fell in love with the Bad boy 9 as they had it at a local bike shop for $574. They only have medium and small left, but the lady i dealt with suggested i go for a large, being 5'10", but she did say i am either the top end of the spectrum for medium, or the bottom of the spectrum for large. My question is, i feel like that price on the bad boy is a great deal. Am i correct about that as i am brand new to bicycles? Or should i go for something on the cheaper end, closer to what i wanted to spend, in the Trek fx 7.1 or 7.2?

Please help!! Thanks!!

I know nothing of this bike, but the price feels like a winner!

You want a bike that fits. Bikes have multiple adjustments so that they can fit different people. Your LSB is right that you are probably in the middle zone between a large and a medium. Adjusting seat height is easy, so that won't be an issue. If your inseam is 30 inches, then you will be able to stand over the bike comfortably. If it's longer, you can raise the saddle. The issue will be the length of the top tube. If you have average or short arms (32- or 33-inch sleeve length), then the medium is probably your best bet. If most of your height is in your trunk and have longer than average arms for your height (34-inch sleeve), then maybe a large is better. Here's a test: Place your elbow at the tip of the saddle and reach toward the bar. If your palm reaches the stem, then you're good. If it goes beyond, the bike is probably too small; if it doesn't reach, then probably too short. This is an inexact method but gives you a general sense. Try it on several bikes.