I don't claim to be able to tell the difference between a cheap bike and an expensive bike. Stiffness? Vertical compliant? Mostly words. Today I test rode a Supersix and a Synapse. I could certainly tell the difference in how much of the road was transferred to my hands. I my string of test rides, I rode an Synapse Red and today a Supersix Di2. I don't like SRAM doubletap (smaller hands). I had a heck of a time shifting the FD to the large right. But the Di2 was really nice. Just a little bit of pressure and the bike shifted smooth as butter and quiet. The 105 was noisier and felt rougher. No hills any where near my test ride, though. If it were me, I would go for the Di2 instead of Red. I was so impressed with the smoothness of the shifting I would have been tempted to spend more money for Di2, but it's not offered on the Synapse.