I am 5'11" with a 31-inch inseam (pant size). My 7300FX is a 20". The 17.5 felt a bit small. I have a clearance over the top tube of about an inch on the 20-incher when I dismount. The fit feels pretty good, though I am not 100% sure whether I am in the most ergonomically correct state on the bike. It it matters, my upper body and arms are fairly long.

The bike is light and very good. It is a good commuter. If speed is your primary concern, a road bike may be better.

Re: "I am 7 feet tall (1.80 cm)". 7 feet would put you around 213cm. Do you mean 6' and 180cm?