IMO cognitive behavioral therapy is a lot more useful than talk therapy but it all depends on the individual. Even talk therapy is better than no therapy whatsoever. Especially towards the beginning of your treatment.
Cognitive behavioral therapy is very uniform and structured. It is pretty much the same for every patient and so it lends itself well to statistical studies. This is a major reason there is such a significant and unambiguous body of evidence supporting the use of CBT.
But the structure of CBT also makes it fairly short-term, after which time you will see little to no improvement with continued therapy.
Interpersonal talk therapy, on the other hand, is highly individualized, and this is largely the reason it doesn't have the same statistical support that a uniform and structured therapy like CBT does.
Intuitively though, if interpersonal therapy is effective with any particular mental disorder, it would be social anxiety, for obvious reasons. It also helps to have a sort of "coach"/"sponsor." Personally, the experience of being able to just be myself as a person without being judged is very rewarding, and helps boost confidence, which most people with social anxiety are severely lacking.
Don't get me wrong, I've been helped by CBT too. Not so much with anxiety, but it's really helped me to take a step back and look at my thoughts and motives when I'm angry, for instance. I DO think it's also a very valuable part of successful treatment.
Even 2 years ago I would have been of the opinion that CBT is far more useful, as I'm the kind of guy who needs evidence. And while I've personally found it to be useful, as mentioned, I was surprised to find for myself the value of talk therapy with a good and caring therapist. I still often feel compelled to stick to the evidence regarding the benefits of different therapies, but in reality it's impossibly to conduct studies on such individualized therapy to the same scientifically rigorous standards that have been applied to CBT.