I have a return to tank system. It was fitted by Omnipole a few years ago. Basically, there is a t-piece on the pump to provide a route back to the tank for the water. Further up the return pipe is a tap. Close the tap and you have a full flow. Open it fully and it nearly all goes back to the tank. Somewhere in between is usually best.
I believe it does mean that the battery is used more than with a varistream (though I've never used one). However, there's no reason it shouldn't last the day - especially if you have a split charge relay fitted. I tend to have a two battery rotation. One in the van, one charging at the mains. Obviously it's far better with an intelligent charger as the battery doesn't get cooked and the electricity cuts out when it reaches maximum charge. I switch them over periodically. Another good thing about having a split charge relay is that it helps to squeeze more from the batteries. I say this because even when the batteries are on their way out, I can just take two old ones out with me and get away with it. by switching them. If they start to struggle too much, I can just run the engine a while.
Apart from that, if there's no Varistream, it's one less thing that can go wrong.
I really can't compare though because apart from a few weeks at the start of WFP, I've only ever used the return to tank method. I may have this wrong but I think return to tank is easier on the pump's pressure switch.