The 24 valve utilizes the VP44 fuel injection pump. The VP44 isn't known for its 'reliability.' per say... and does NOT enjoy dirty fuels/waste oil/alternative fuels.
The VP44 doesn't enjoy cold weather starts compared to a P pump... let alone a VE rotary pump which is considered the cold weather king.
Also the added complexity of potential electric lift pumps etc all add to make the mechanical 12 valve (P-pump or VE rotary) more and more user friendly.
Tack that on to the fact that there were some block issues on the 24 valve early on (research "53 block issues" ... casted 53 blocks were plagued with cracking).
And only using 1 wire sure cleans up an engine bay. I was very happy on how mine turned out and its drive-ability and modest power bump. (My engine has a slight bump on the power screw and a 3200rpm governor spring installed and that's it)
67' M715/5.9 Cummins/ZF5/NP205