I don't know in detail, what you mean when you say 'tightrope surgery'. I'm assuming its an extra-capsular technique, in which a nylon cord is placed around the joint, and securred. (something like the DeAngielis (spelling?) technique.)
The articles I've read (research articles) seem to indicate that long term, the results of the two surgeries are comparable. This runs counter to what the orthopedic surgeons I've spoken to have said (I've spoken to two board certified orthopedic surgeons about it). The widely held belief (which I'm not sure if its backed up by any data) is that long term, you end up with more arthritis with the nylon cord technique, relative to the TPLO. I think return to first use is faster in the TPLO, although the total repair time is somewhat longer.
One 'rule out' for the nylon cord technique, is the dog has to be small enough so that the cord doesn't break too soon, otherwise you're back to square one. (Where I am, the absolute upper limit is about 75lbs, due to the heaviest weight nylon cord and fasteners that are available).
My own dog had the extra capsular repair, and while he hasn't returned to 100% function, most people are unable to spot the lame leg (There is evidence going down stairs that he isn't 100%. I can detect a slight abnormality at other times, but I don't think anyone else would be able to. There is also a marked thickening around his knee, which is to be expected).
I'm a vet student
I've assisted in both TPLOs and the extracapsular technique
I have a special interest in orthopedics
My own dog had his cruciate repaired about a year and a half ago.