Hello
Can't comment on harps gut, but since 10 months i have the Aquila reds on my 6 string tenor gamba (G/C/F/A/d/g). Before that, I had Kürschner gut strings. Coming from double bass and knowing how far away gut alternatives are from gut, no matter how gut like they are advertised, i have to say that the reds come pretty close. I think i would fail a blind test, if it wasn't for the rough surface of the reds. I really wish they could make those reds for double bass as well.
Tuning stability and tunability are superb.