The MES and the XLE are rated at different pressures and they have different daily rated capacity so you can't easily compare them by just looking at the specs. They look to me like they have about the same capacity when operating at the same pressure, so they will be priced about the same. The pump, membrane housings, etc are pretty expensive so I prefer to spend a little more on the membrane so I can run a smaller unit. The NF are more expensive because they have more capacity.
Dave
Leader 1/2 pint - Kawasaki Mule - Smoky Lake Filter Bottler
24 GPH RO, 2 1/2 x 40 NF3 (NF270), 140 GPH (Brass with no relief valve ) ProCon pump
2013 - 44 taps - 16 gallons syrup, 2014 - 109 taps - 26 gallons syrup
2015 - 71 taps - 13.5 gallons syrup, 2016 - 125 taps - 24.25 gallons syrup
2017 - 129 taps - 17.5 gallons syrup, 2018 - 128 taps- 18 gallons syrup
2019 -130 taps - 18.5 gallons syrup, 2020 ~125 taps-19.75 gallons syrup