Well I went 10 years without a tail kit, so it's not 100% necessary. I also skunked my skins a half dozen times. Had to put them in a jacket and warm them for 30 minutes to get them to work. Voile straps saved my butt a few times too. If you don't have any of those I recommend buying four in the 24" length. I've used them to secure skins, tighten a boot, make a broken ski pole usable, even to make a broken binding usable. They can really save your bacon when you are out in the backcountry.
If you are not worried about the costs, go with the Voile skins and get a Spark Tail Kit. It's nice having the nose attachment already pre curved and such. If you are looking to save a few dollars, go with climbing skins direct. You'll have a tail kit that comes with them and the skins work just fine. In a lot of ways they are easier to deal with than the Voile skins. They just don't look as nice once you finish modding them for splitboard skis is all. At least with me it worked out that way. I of course have zero artistic talent. I can't draw stick figures for fuck's sake...
the tailkit is like a $20-40 bullet out of a $500-$1400 magazine you'll be shooting (if someone buys a new split.)
also, you can do just fine without the little plastic strappy thing that attaches the tailclip to the skins... on a split they connect at a funny angle so dialing in that strap can be a bitch - i just used elastic/bungee style cordette with my G3 tailclips and they seem to stay on fine - although its a new setup and i haven't put a ton of miles on it yet.... but its fine
G3 makes very supple skins. They are not as durable as the Ascension skins, but they are so much easier to deal with. As far as how they climb, I believe the Ascensions to be slightly better, but maybe not. Something I seem to remember reading in Backcountry mag when they did a skin comparison.