I agree with not starting with the RPi (to avoid the complexities of the Linux kernel), but I started with the PIC and SX series (before Arduino was a thing) and wouldn't recommend it anymore. If you want to learn an assembly language and twiddle registers then maybe you'd like the PIC, but I don't think it's more "professional" - virtually everyone uses C if at all possible at this point, and the AVR (or bigger PICs) are just as "production-ready" as the old PIC16F series. And you can still twiddle AVR registers with C if you so desire.