Assuming the same quality material is used in the M16 Bolt and Carrier Assembly as in a AR15 B&C Assembly,
Is there a particular reason to use the M16 B&C Assembly beyond the slightly higher weight?

Slightly heavier is all.

Some old Colts had sear blocks that required different carriers.

I don't know why they still make SA BCGs. Must be cheaper to make.

Out of a dozen, I have 2 that are SA cut.  They are DD chrome, and it is the only way you can get them.

They work just fine.  As long as your gas port is smallish

I did not believe the hype, but on one of my 12.5s I played around with a Spikes FA and this DD until I got what wanted with springs and buffers.  The FA Spikes would throw brass at 3:00 with a carbine spring and buffer, and the SA DD would throw it at 1-2:00.  I put in a H2 and she is solid at 4:00

Not starting a ejection pattern shitfest, I honestly don't care, but with a proper gas port it was interesting to see the difference on common ammo.

I like the DD chrome BCGs.  They look awesome in a retro

The M16 carriers have a shrouded firing pin so the hammer doesn't catch on it and bend the FP retaining pin.

A lot of AR15 carriers have them also.

Aren't pretty much all AR15 carriers made like that these days?

The ones I have seen.  The DD definitely is

Out of all my rifles I only have one that isn't fa style.

I know some people get worried about having a fa in a semi gun but they are fine to own.