If you are willing to buy a MCP hardware... get one that is fully supported for xplane, otherwise you will end up having a hardware partially useful and they are not cheap.
Most aircraft no matter its complexity uses default xplane commands/datarefs for IAS, COURSE, ALTITUDE, HDG. But all payware aircraft that mimics real life birds uses extensive proprietary custom commands/datarefs for VNAV, LNAV, CMD A-B, CWS A-B , FD switches, AT switch, VS display & wheel, N1, AP disengage, light status, etc. thus they will not work unless your can program your MCP on a per aircraft basis.
That being said, the most important thing you have to look at for your decision is: per aircraft support vs platform programable support
I mean, if you get a MCP that the developers made internal support for specific aircrafts, then be sure you will not run your precious and expensive MCP to any other cool addon that releases until they decide to support it, and you even risk some features stop working on your existing aircrafts during aircraft's developers updates until they update their code as well.
What you need is a MCP having a xplane interface tool for you creating on a per aircraft profiles to map your mcp hardware to differemt aircraft specific commands/datarefs.
Unfortunately i learnt that the hard way.
Bought my Goflight MCP PRO without much research/knowledge a year ago, sooner i realized it had no interface for xplane, some free developers managed to create plugins that supported specific aircrafts of their interest. Those developers moved on some time ago, and once those payware birds got a few updates they stopped working, crashes and many issues that forced me to retire my MCP PRO.
Fortunately god shined us a few weeks ago and Pollypot released their Goflight intergace tool for xplane (payware), but dam, this app is so cool. It has a graphical interface were you create profiles on a per aircraft basis, and you assign any button, light, switch, rotary, display, etc. of the MCP PRO to any aircraft custom command / dataref. So it supports ANY aircraft and you can keep tuning it by yourself when new aircraft releases or existing ones updates. You can also import/export profiles to share the community not requiring everyone creating their own profiles.
I am not telling you go and grab goflight + pollypot, that is your call, could be other alternatives to compare. But be sure you get what you need, otherwise you will get a course/hdg/ias selector instead of a full working MCP to any aircraft as you expect.
hope this helps someone.