Welcome to the board Paul, WFP systems are a bit like computers, everyone uses the same bits, and stick their own name on them. The most expensive isn't always the best value, They have to recoup their huge advertising costs by adding them onto the price.
I would say that the most important priority is to get the tank fitted properly, so make sure that whoever you buy a system from has the knowledge in how to do it.
I would go for the cheapest system, providing that they can guarantee that the tank is fitted safely.
If you search on here there are posts on how a tank should be fitted, ratchet straps attached to the anchor points would be useless if you ever had a head on crash.
Good luck.