ProcessWire is easy to get the hang of. If your going to build sites for clients, you will appreciate the differences soon enough. Come on in, the water is nice.
BTW: i just finished moving the last of my client sites off MODx (started on 0.95). Most of them I converted on my dime. I did it because It saves me time and is easier for them to manage content. No more dependance on custom modules to get my sites the way I want. Have most everything I need in the core. Dumped drupal for many of the same reasons too.
I used to think lots of great third party modules for *some cms* saved us time. Not so. The upgrade problems alone cost us more than the coding in PW.
Learn to code. It's a skill that won't be replaced.