One main reason I chose the MSP430 was for the FRAM. Photon stores all its state (ie the photo ring buffer indices, and user settings) in one big FRAM struct, which can be read/written just like RAM, but persists across power cycles and crashes.

Another reason was MSP430's low power consumption, but like you said it sounds like ARM has caught up.

Would love to hear about alternative designs -- are there low-power ARM chips that have something like FRAM and don't require erase/programming dances to write data?