I've owned both with the LS-26 being the first ARC preamp I ever purchased. The Ref 3 is a worthy upgrade, especially at the cost differential if buying used. It dug out details the 26 couldn't reproduce. I did email a reviewer a few years back who reviewed the LS-27 and thought it, in his opinion, was better than the Ref 3 but not by a whole lot.
I will say I didn't own the Ref 3 long enough to acquire a Tung Sol 6550 from the 50's that is reported to be the "must have" tube in the Ref 3.
I will say I didn't own the Ref 3 long enough to acquire a Tung Sol 6550 from the 50's that is reported to be the "must have" tube in the Ref 3.