So, I was in this position a few weeks ago with having to decide between the CS3+ or the ESU ECoS (50210). For me, there were a number of reasons why I chose what I chose. I read this forum before I made my choice and looked at what you guys all had to say. Then I did more of my own research online and also weighed my own experiences with the CS2 that I have owned for 10 years. First off, I have owned the CS1 and later the CS2 and I have never been really impressed with either. I sold the CS1 years ago, didn't like the fact that Marklin left everyone who bought it hanging so to speak because they soon stopped offering updates for it, and you were left out in the cold unless you sent it into ESU to be reloaded. Despite that, I bought the first CS2 when it arrived in 2008. I was never in love with the CS2, the processor was extremely slow even in 2008, and updates over the last 10 years did little to help the software's glitches and issues. For example, I still, 10 years after I purchased it, have many menus and prompts which are in German and not English, despite the fact that I have the CS2 set to be in English language mode.
I recently purchased some new loks, and started reprogramming the locomotives' CV values using the CS2. That was a big mistake. No matter what I did, and how I did it, I could never get the CS2 to reliably work at changing CV values. You select the CV, change its value to what you want, hit program, then hit the program to the track button with the arrow pointing to the track, and it would work sporadically at best. You'd have to do the same process 5, 10, or 15 times to get it to finally work. I actually had much much more luck using my ancient Marklin MS1 controller to change locomotive addresses than I did with the CS2! It worked very well, and I soon stopped using the CS2 for changing addresses. But I then ran into an issue reprogramming digital decoders and I needed the CS2 to get more in depth, but again, the CS2 did not work reliably. So in desperation I emailed one of the largest Marklin dealer/service centers in the United States explaining the issues I was having with the CS2, and asked if I should purchase a CS3+ in order to finally get a machine which would work. I was shocked at his response, he said: "you need to find someone with an ESU ECoS that you can borrow or use to do all this CV work". Keep in mind I had NEVER mentioned the ESU ECoS to him, I only asked if I should buy the CS3+, and essentially he said get the ECoS instead. Also, keep in mind I have never owned any control system except Marklin, I have never owned any ESU devices except the decoders pre-fitted in loks, and FYI around 90% of my 70+ loks are Marklin, many of them are MFX.
I then talked to another huge Marklin dealer in Germany regarding the same question and they told me that they themselves use the ECoS for their store. That to me said a LOT, and sealed the decision for me. So, as you might've already guessed, I purchased an ECoS (50210) instead of the CS3+. I can only describe the change as going from the dark ages to the 21st century. The comparison from the ECoS to CS2 isn't even a comparison. The ECoS is so much faster and more intuitive, if you think a button does a certain thing/function, it likely does it. That's seldom been my experience with the CS2, it's one of the most UN-intuitive devices I have ever used, but you force yourself to learn and get used to it. The ECoS makes reprogramming decoders and changing CV values so easy compared to the CS2 that you swear you must be doing something wrong, but you're not! It's just that much easier and faster. To me, the CS3+ looked like an amazing machine in videos and reviews, with the ability to drag icons and items, pinch to zoom, etc., but I know that the software is going to have a lot of issues, Marklin has had a decade to fix the CS2 software bugs with updates and they never did and it's still awful. I have no reason to believe that they'll change their ways now since they never did in the decade prior. I also suspect that while the CS3+ is certainly powered by a much faster processor than my old CS2, it will likely not be as good at programming and working CV values as the ECoS. ESU knows their decoders and software, and when you own an ECoS it really shows. I love my new ECoS, it's so nice to have a machine that when set to English actually has all its menus and prompt boxes written in English!!! Imagine that?
Looking up menus of all your locomotives is fast and easy with ECoS, and one other little detail that I liked was that on the menu list of locomotives you have saved on the ECoS, that it shows you the address number next to the name. It's nice that you can just see that, instead of having to select the lok, hit the wrench button, and then see the address like on the CS2. And even though money was not an issue for me, and I could have easily afforded the CS3+, I really liked the idea that I could get an ECoS for less than $700 with the transformer included in that price, the CS3+ with transformer would run me close to a grand at the cheapest. Yes, the graphics and display are more fancy shall we say on the CS3+ than the ECoS, but in my opinion, I want a control unit that can control and modify trains reliably, and some of the stuff on the CS3+ like MFX+ capabilities seem like a gimmick to me. When I'm running my trains I'm looking at my trains, not a fake engineer's cab on the screen!
So, all in all, I still own the CS2, and now I also own the ECoS, and when I had to upgrade and choose between the CS3+ and ECoS, I chose the ECoS and could not be happier. It's a very fast and intuitive machine that does what it's supposed to do incredibly well, which is control/modify trains and accessories. I really feel I made the right choice, but hey, do what you want to do.