Using a phone for a primary control device is a bad idea. It always has been, it always will be. You can accomplish some cool things inexpensively on a phone or tablet and apps on those devices make great supplementary control. But there should always be a primary dedicated control interface available for a system.

Being you have been using an MX-850, I'll guess that you are just looking to control a small local system (TV, amp, couple of sources). Meaning not trying to control a whole house, lighting, HVAC, and other home automation systems throughout the house.
So in that case, the Harmony line of remotes should be fine.

If you want to get one of the newer URC Complete Control remotes (MX890, 990, etc.) and do the programming yourself, you will need to make sure where you buy it from will supply the programming software to you. It does not come in the box and URC generally does not give it out to consumers directly. Many places (especially non-authorized discount houses) will not supply the software.
I think there is a way to import parts of the MX-850 programming into the CC software but it has been many years since I had to do that. Being how completely different the layout is going to be, it would probably be best to just start from scratch on the new remote.