I guess if I was going to look at the LPC9xx parts I could just as well look at the Cygnal 'F3xx parts. THey would work well too.
Absolutely; however the LPCs are sooo much cheaper. I approached the SILabs distributor "since I am using thousands of your f12 chips, do you also have a LPC equivalent in price" They just shrugged.

Another advantage of the LPC is the codearchitect, free from esacademy. To do what you need (IIC to PWM) 5 minutes with codearchitect will generate 75% of the code and all you have to do yourself is the main loop and a few other things.

Erik