This style of connectors has been around for years. I have a site up here and that it riddled with these type of conncectors. They have teeth that bite into the wire. I do not like how they make contact the wire. They appear to have minimal surface contact and damaging to the strands. there has been a few connectors ther have failed over the years. Not a good thing.
I typically use a good ol' fashion split bolt. I put a layer of cheap tape sticky side up. Then I wrap the split bolt with mastic pad the rap the pad tightly with a good quality tape. If the split bolt needs to be removed, all you have to do is run the utility knife down the side of the split bolt and the covering peals back like a bananna skin and just as easy. I have never had a failure with this type of setup.
I have also used the Polaris for the first time just a few months ago. They are little spendy but make for a quick splice so the added cost may be warranted. The only problem with them is the are very limited on the wire size so on a service rig, you have to carry more of them then split bolts in order to cover a same range of wire sizes. Tapping different size conductors are difficult too with Polaris connectors unlike with a split bolt and you do not have to cut the cable.