Linear magnetic field position sensor output: PWM vs. Digital
I haven't read the data sheet in detail, but you barely need any code on a microcontroller to bring in the PWM signal.  A capture interrupt is just about all you need.  Can't get much simpler. No protocol to match, no baud rate ....

If you need to bring the data into a computer, however, you'd certainly use the serial protocol.

Read carefully, though.  There may be ways to bring in MORE data or read settings and the like over the serial protocol that aren't accessible via PWM, and you certainly can't send any config info to the chip via a one-way PWM, so if you need to talk to the IC, you may have to implement a serial port anyway.