I demo'ed both Indra and Proteus Provectus at the same time in my system for approximately three weeks - thus, while I cannot comment on the basis of being a long term owner of each, I do have some comparative experience (I also still own a pair of Indra Betas, so do have some longer term experience with that cable). Thus, please take the following review with that in mind.
The Indras do some things fantastically well - better than any other cable I have heard. Its imaging, particular in the expansiveness of soundstage, as well as the dimensionality of images within the soundstage (i.e., the extent to which individual images within the stage have depth and volume), is pretty special. Resolution of low level detail is also outstanding, as is transient attack and decay. It is also a very neutral cable - no rising top end, no midbass emphasis.
However, if you are looking for something that adds some "richness" to your system, a la Siltech cables (which I also own, so I do not mean to criticize), then this is probably not the right cable for you. I have also heard from other owners that too many Indras in a system might be too much of a good thing, but have no personal experience with that.
The Proteus Provectus disappointed me to a certain extent. I do not mean to say it is a bad cable; in fact, it has no glaring weaknesses. It did everything reasonably well, and no individual charateristic called attention to itself. However, from a tonality perspective, it had a very different presentation that the other Purist cables I have used (e.g., the old Colossus back in the day, Aqueous Anniversary, and Dominus / Dominus RLS). Provectus was a neutral cable, but lacked the midbass to lower midrange magic that especially Dominus had in my system. It images reasonably well, but no where near the Indras. Dynamics were OK, but again, fell short of the Indras, Dominus, and other cables I have had in my system.
Surprisingly, the cable of which the Provectus most reminded me was the Silversmith IC cable. While the Silversmith might lack a touch of bass weight compared to the Provectus, they were quite similar in other characteristics. However, given that the Silversmith is less than half the price of the Provectus, I found it to be a better bargain.
To summarize, if I had to pick between the two, I would go with the Indras - however, if you upped in the Purist line to Dominus (or, from what I have heard, the new Anniversary), you really could go either way, depending on what your listening priorities are.
Unfortunately, I have no experience with Kubala Sosna Emotions. I have some Fascination speaker cables I use in a second system, but don't think that gives me enough basis to offer an opinion in terms of what you might be looking for.