I use an S5 for work, but have an X1C at home, and the difference in quality and ease of use is noticeable. Not to say the Bambulab is perfect: the AMS is just as quirky as the Ultimaker Material Station at times, particularly withdrawing filament, but the way the X1C handles faults is brilliant, and print saving. I believe that the bigger players in the market have to rush to catch up.
Saying that, most issues I get with the S5 are user errors (I still make those even after five years of experience! ALWAYS check your previews before sending to print!), and the S5 is a proven workhorse where the X1C is still new... But if I was compiling my additive manufacturing project now, I'd be looking at an X1C over an ultimaker every time.