I've found there are advantages to both. On a simple set-up with one printer with direct connection, YaST is fine, and it has a nice test page. However I maintain a small office network with multiple printers accessed via a print server, and for that CUPS is much better.
Occasional AC supply glitches cause the router to reboot, and sometimes the print server as well. When this happens CUPS gives you more error information than YaST, and I've found it easier to get things working again. The only downside is the CUPS test page is not very informative, compared with YaST.
In the long run it is whichever you feel most comfortable with. The great strength of Linux is that there are multiple tools for the same job, so you can use the one you like best.