Replacing drivetrain on Defy. Its a 2012 version, with Ultegra 6750 chainset, and 105 cassette and chain. Have ordered new 50/34 rings from action sports and 11/28 cassette from wiggle. I actually have a new unopened 10 speed ultegra 6701 chain – will this offer any benefit over a 105 chain ?

You’d see little benefit between 105 & Ultegra IMO especially with a chain.

It will be all of about 10g lighter. Other than that, no benefit whatsoever.

Chains are the one area where I advocate spending as little as possible, and just changing them regularly. Contrary to what manufacturers might say, a brand new cheap chain will shift much better than a high end chain with any amount of wear in it. With chains the mantra is “buy cheap, replace often” if you want a tip top performing bike.

Thanks both