If you absolutely had to sell off one to get the other, then I guess you have to.
If you just do not enjoy using a non-metered detector, then I guess you would have wanted to.
If something in print on a forum convinced you that the new X-Terra 50 was the ultimate detector for any and all applications, then somebody did quite a sales job!
Otherwise, I am saddened to hear that you parted with the Shadow X5.  It is quite possible one of the best, multi-purpose detectors available.  I can't see anyone coming out with anything that could replace it anytime soon, so my Shadow X5 and 3 coils remains a key part of my three-detector battery.
On the other hand, I am happy top hear that you're buying a new Minelab X-Terra 50 because I know how well this detector works.  I know how easy it is to learn and use.  I know quite well how 'fun' the X-Terra 50 is! 
It's possible that the X-Terra 50 offers just what 
you have been looking for in a detector.  I know it has some of what I have looked for and, if you get as much satisfaction out of your new detector as I have been, it will be one you definitely won't be selling or trading off in the near future.
Happy Hunting!
Monte