Hi all, I'm currently building up a road bike and need to choose the groupset that'll go on it. I can get a used(less than 1,000 miles) Dura Ace 7900 Groupset for around $300 from a friend and a new Ultegra 6800 groupset for around $380, also from a friend. My wheels are only 10 speed compatible so if I buy the 7900, I would have to upgrade the wheels(which are pretty bad anyways). What are your thoughts on those two? I can't seem to find a decent comparison between the 6800 and the 7900 anywhere online!