I was in your position about 3 weeks ago.
I decided to go with Premier for 3 reasons - First, Kencove was out of stock on the fencing that I wanted (and still are). Second, Premier's fence seemed to have "stiffer" vertical stays. Third, FREE shipping from Premier on the fence and charger (Kube 3000) and they also ship the same day if you get your order in by 1:00pm CST.
I also have deep sandy soil so I went with the double spike but I did not go with pos/neg. I've used electric fence before (horse) and haven't had a problem with grounding but then we don't have beach sand here
The double spike line posts work great (I was worried about the sand) - I have had to reinforce the end sections with step in posts and I've also had to use some fiberglass rods between the line posts due to the fencing being on a hill causing some slight sagging but I expected that. I wouldn't have to use the fiberglass if I was fencing in a flat pasture the fence stands straight on it's own with the vertical stays. I bought the step-ins and fiberglass rods at tractor supply MUCH cheaper than ordering through Premier.
I purchased a plug in charger and mounted it in the barn then I just ran insulated wire to the fence (I called Premier and followed their advice on the wire) - I left the spool intact so I can move the fence as far or close to the charger as I want - this way I don't have the extra expense of batteries and have a much stronger charge. I also bought the insulated wire from tractor supply and again MUCH cheaper than through Premier.
Anyway - probably more info than you wanted LOL! but this is my recent experience with Premier - it's a quality fence, easy to install and works great.
HTH