What Trek 7.1 FX frame size do I get?
I'm new to this community and am really excited to be purchasing my first hybrid bike for commuting (I previously used a cruiser bike but quickly outgrew it). I want to buy a Trek 7.1 fx bike as it's in my price range and exactly the kind of bike I'm looking for, however, I'm very confused as to what frame size I should get.
I've gone to look at and test ride the bike on a few different occasions and I found that every time I went the employee would tell me I needed a different size than the last time I was there. Sometimes I was recommended the 17.5" size frame, and sometimes they would tell me I needed the 20" size frame. I'm only 5'9, 155lbs but apparently my legs and arms are proportionally longer than most people which is why I'm always recommended something different. My height tells the staff that at 17.5" would be ideal, but my leg/arm length tells the staff that I need a 20" frame.
As this is my first hybrid/commuting bike I don't really know how it's supposed to fit me. While both frame sizes are comfortable they affect the way I sit on the bike and I'm not sure which is best. While I ride more comfortably upright on the 17.5" frame my legs feel a bit squished even though they don't hit the handle bars or anything - is it normal for them to feel this way? The 20" frame feels beter on my legs but makes me feel like I might be leaning over more than I should be. In the end the staff say that the decision is up to me - whatever I find most comfortable and it's a tough decision for me to make as their both comfortable in different ways. I want to make sure I pick a bike that I won't start to feel really uncomfortable riding after a few months.
Does anyone have any suggestions for me as to which frame size I should get?