I'm 5'6 with a 29.6 inch inseam and I chose the medium. I'm going to throw on a 110 stem on there and based on the measurements, it should fit nicely. Just as a reference I rode a Tarmac size 52 with a 120 stem and it was perfect. Really depends on your riding style I suppose. As far as just measuring the top tube, I'd say go for the M/L frame unless you have short legs for your height in which I'd go for the medium.