I think I will get the X16 firstly. Once I get the hang of the programming, I might consider the MEGA65 out of curiosity.
The X16 does seem to trigger my nostalgia on the basis of the architecture and limitations.
The Mega65 seems to trigger my nostalgia on the basis of physical design.
Nothing is perfect, would probably, be without a doubt, happy with either or both.
I like these for different reasons.
X16:
Strictly consistent with the 8-bit experience. The MEGA65 is a bit too much on the modern side.
Expansion slots.
Adds some performance compared to the old computers, and not by too much.
New platform.
FM tone generator.
SNES gamepad support. (USB would've been better though).
The Community.
Omega 65:
C64 compatibility.
Formfactor / Classic Design. This gives some nostalgic feel, because modern computers aren't built like this today.
HDMI output.
Mechanical keys as standard.
I kinda like the idea of a floppy drive. Too bad more advanced features defeats it's purpose.