The most important question is = Do you already have the programming software? AND a login/password for it?
If you don't know what that means, you need to do some reading. A lot has changed this last year at URC. No one is happy about it.[Link: remotecentral.com]
That said, the MX-780 was a horrible remote. Just about anything is going to be an upgrade. The new model MX-790 is a much improvement. If you wanted to go with a rechargeable battery, the MX-890 or MX-990 would be a good choice (990 preferred since its not much more).
The 880 has been discontinued for awhile.
If you are looking at used remotes, note most MX-890 for sale on eBay are the old style with a dimmer backlight. There was a running change that addressed this and the newer ones can be identified by the change in the button text vs the old ones.