Rick wants to get the Google Nexus 6. Leo recommends the Nexus 6P through Google Fi. Nexus is the best choice because it's pure Android with no overlays like TouchWiz. He'll always get the next update of Android's OS because it's coming directly from Google.
GoogleFi is great because it will seamlessly hand off from Sprint to Verizon to T-Mobile -- whichever is best. The service is $20 for unlimited text and voice, plus he'll pay for only the data he uses at $10 per gigabyte. They'll even charge fractionally per megabyte. So if he only goes over by a few megs, they'll prorate it.