Seems like such a simple question yet Answers are far from complete. Allow me to fill in from what I know and experienced since I bought all the models.
MP10w is wireless. You can link them all and they will do different things.
MP10 ES eco smart without wireless
MP10w ES gives you the same as above but adds their 2 special functions for nutrient export. It does long or short pulses followed by something else I can't remmeber. The MP10w ES also gives you a new controller which in itself might be worth it.
MP40w and MP40w ES is same as mp10 as listed above but more powerful pumps. The problem with the MP40's is that they changed the bearing design so that instead of running the bearing all the way thru the shaft (ceramic shaft) and having the shaft supported in both ends like the MP10, they have the entire impellor assembly on a single flanged ceramic bearing. What makes it error prone and fails is that if the thing wears down even slightly due to calcium build up, it can quickly wear out plastic bushing surrounding the bearing, drag the magnetic in the housing, or even lock it up causing the impellor shaft to snap. Very easy to break.
The MP60w is basically a super sized MP10. None of the MP40 problems but with all the benefits of the MP10. MP10 is actually very reliable due to support on both sides and ceramic shaft instead of ceramic flanged bearing. They also improved the flow of the MP60 and also added cooling fins on the motors on the outside. MP60 is a vast improvement over all others. Runs cooler, puts out more water, and reliable. I replaced 2 MP40 with 2 MP60 .
If I were you get the MP10w ES. The wireless allows you to update firmware, bring all units to sleep mode with one controller, and also syncronized the pumps so they act as 1. In my opinion and in my tank , it creates better swells.
You can't update an MP10 but you can go from MP20 -> MP40. But why bother? You can get these used so cheap you may as well just get a used one and be done. MP20 is worthless.