Currently looking at same models to buy. From my recent research, here's what I've learned so far: Yes the M200 is exactly the same as the internet-only Nautilus CC plus. The Nautilus does have a smaller filter capture area, but it has a better suction rate of 4500 gph vs 3750gph for the S200 (maybe 4000?, seen both listed in various sites) and a longer 30 mth warranty (vs 24 mths for S200). However, the S200 has one of its 2 brushes "active," which I think means it rotates faster and maybe scrubs better. It also cleans the waterline, although I've read several customer reviews who say the Nautlus does actually reach the waterline (not sure I care if it scrubs the actual waterline, as this is a minor cleanup). BTW, the S200 is also the same as the Active 20. Both have a higher level wifi model (S300/300i, Active 30/30i) that has better warranty and includes the caddy, and in the 300i/30i, has an extra enhanced cleaning cycle of 2.5 hours and a dual layer filter. But these "i" models are pricey.
For me, although I prefer the lighter weight/bigger filter basket of the S200 (16.5 lbs vs 19 for the Nautilus CC Plus), I am hesitating because the Nautilus has way more great reviews on Amazon (and its twin the M200 has great reviews on Maytronics own site), is the #1 pick on most every review site, and has the better suction/warranty. (BTW, the comparable internet only model to the S200 is the Triton PS/PS Plus, which has very good but not great reviews on Amazon). I guess it depends on what you're expecting to clean/scrub/pick up in your pool and do you need the bigger filter basket of the S200/Triton (need to clean less often with bigger basket?).
Hope this helps
