My son rides a Tarmac SL4 and I ride a Roubaix SL4. The Roubaix is definitely more comfortable on long-distance rides than the Tarmac but that's more to the position than the ride quality. Compared to the Tarmac the Roubaix is more upright and consequently a little less rewarding when you put in an effort. The ride feel is similar to be honest, both are very smooth bikes especially if you fit them with a quality tyre like a Veloflex Open Corsa or the Vittoria equivalent and some latex inners, run at about 90 lbs. Specialized bikes have a flip-flop stem and clever eccentric shim, which gives you quite a lot of adjustment to the bar height. For next Sunday's Cheshire 100 I will be flipping my shim to get a slightly more upright position.