OP, think about your network/carrier coverage in your "home" zone and out-of-town/abroad usage ?? Assuming your personal device & current provider offers good coverage and whether you are planning to upgrade/trade-up for a newer device soon - I would go to the opposite (GSM/4G-LTE via-s-via CDMA/LTE) for redundancy to cover the bases. A good, reliable & fast dual-ports + charger would simplify taking along multiple accessory gadgets, including mobile ones.

If you are leaning toward GSM devices, think about Sim cards, using the same sized one on both will give you easier backup ability to switch them if one of them - especially the "work" phone malfunctioned. When I'm on an extended/oversea trip, I carry a 3rd. "dumb" phone, unlocked quadbands with WiFi access, and the extra charging/data cable go into EC gadget pouch (oooh, the Garmin GPS has been in exile for 5+ years)

+1 on the Google Nexus series without carrier bloatware, runs great - especially rooted, mine is on stock firmware with just Xposed & Gravity Box & as a WiFi hotspot if necessary and good for 2+ days of moderate usage. Mrs. L's in white & mine in black, and different cases to avoid mixups. The Moto E's, factory unlocked & no contract, 4GB model is $129 only - it is a bargain with choice of US or Global GSM firmware - the downside being that Androids don't retain high resale values and/or at trade-in time. I just hold on to them as spares & loaners for others, and older ones are donated to charity.