Just a quick note since some people may have forgotten....not everyone is as proficient as you(the generic "you") are at XXXX. I know, shocking isnt it?
SXE MX6....the answer to your question should be the same as any other thing out there. In no particular order....
-what are your needs for the car(today and in the future)?
-what is your budget?
-what features do you want/need("wants" and "needs" are two different things)?
-how adept are you with regards to DIY?
-do you have a timeframe for what you need?
-will the unit you get be upgradable/suportable in the today and in the future?
-what kind of knowledgebase exists for the unit that you will chose(online and locally)?
Theres other criteria out there, but that should be a pretty good framework to find what you want.
Good luck on your choice....whatever that may be.
Gavin