Let me first say that none of these Android/Windows CE head units are perfect..some have more bugs than others, but if you can work around-or with-those issues, they can be great head units for the money.
I currently have an Eonon GA5150F in my '04 330i ZHP. This is the full Android 4.4.2 based head unit, and overall it works very well. I cannot use the automatic headlight mode on the LCM, as leaving it in that mode keeps the head unit on at all times. That's not a big deal with me, so I just manually turn the headlights on and off. Besides that, I haven't had any real issues. All of the functions work properly. The FM/AM section does leave a lot to be desired, and I am using the correct antenna adapter with the proper power connection for the antenna amplifier in the C pillar. I don't listen to much FM so it isn't a big deal with me.
The D5166X looks to be the older unit that was based on Windows CE, if I am not mistaken. I do hear many complaints on the older Eonon head units that are on the Windows CE platform. In general, the Android based units are newer and seem to operate better overall. I don't think anyone here has mentioned it, but Eonon has a brand new head unit available for the E53...the GA6166F that runs Android Lollipop 5.1.
Eonon GA6166F | BMW E53 Android 5.1 Car DVD | BMW E53 X5 Navigation | Android 5.1 Car GPS for BMW E53
After I get the motor replaced in the '01 X5 3.0i I purchased for my wife, I plan to install one of these once all of the other primary issues are attended to. The X5 has the low end factory head unit, so it should be an easy swap. Once that is installed I will try to update everyone on how it operates.
So long story short...in my experience, stick with the newer Android based Eonon head units. They aren't perfect, but they are better than the previous models they offered.