Not really true....
The ECU can adapt a little but it is not designed to adjust to major performance changes in the engine. This has been hashed out over and over and yes, I know there are some vendors that believe that it is not needed. However, there are many more that firmly believe that it is needed. Just to give you an idea. I added a 15% pulley to my MINI and ran it without a remap for a few days. Every time I got out of the car, I smelled fuel. Not a good sign. After the remap, performance and drive ability increased there is no doubt about that and the fuel smell is gone.
As for the choice between
JCW and MTH. Yes, there have been changes in the MTH program. The cost has gone up a bit and any updates will cost you a bit more. Overall, they are still cheaper than most out there and in terms of what you get I think that it is still worth it.
I can't speak on the
JCW, especially if you are getting more of a custom tune. It sounds comparable to the MTH on that level and might well be worth it. Tough call....