I wouldn't say way better, although I have never used one. I have read the install instructions though and they seem harder to install than a helicoil, and they were more expensive as well. I have never had a helicoil back out on me. Once they're in, they're in as the coil is oversized and the install tool pulls them in place.
If I had a really tough repair, like an SAE boss o-ring fitting, I might consider a solid insert like the keensert. A helicoil wouldn't be appropriate as the top of the threaded hole needs a taper to contain the o-ring and seal it. But there aren't any SAE boss o-ring connections on my Stovebolt, so I'll stick to helicoils.
