I wouldn't say resin only would work out hugely more expensive, 150 isn't massively high for resin only (below 100 would be better.)
if your on a meter could have benefits going resin only, no waste water, quick filling, can fill from customers too if needed.
I would now always go RO route tho, if gonna b window cleaning long term wfp might as well commit to it and get the proper kit if can afford to.