Well, I don't know about "detailed", but:
The software improvements can be had in the 49G+ by upgrading the ROM to the latest version.
Improvements in the 50G hardware:
You may prefer the color scheme. Or not.
The 50G uses one more "AAA" cell, but that may not affect battery life much, depending on your usage. It's slightly heavier.
It can be powered from the USB port, so if you connect it to, say, your computer, you can use it all day with no battery drain.
The keyboard is as good, and possibly is better, than the last generation of 49G+. It's definitely better than any early 49G+.
It has a serial port for communication with specialized devices like GPS units for surveying, or any other use you may have, as long as you have the required, not-supplied, special non-standard cable. It's still better to use USB for communication with most computers.
In other respects, there's not much noticable difference; no speed improvements, no more RAM or Flash, same size and quality screen, etc.
In short, if your 49G+ breaks, you can feel a bit better about replacing it with a 50G. If you don't need the serial port, then there's probably no pressing need to upgrade. This is, of course, a matter of taste, so you may decide differently.
