Carbine vs A5 buffer

I’ve been trying to read up on this as much as I can. There is great info but I’m just trying to get a nice, clean understanding.

I know the buffer travel is the same with either tube/buffer combo.

It would seem the A5 allows for a heavier buffer and a spring with a higher spring rate but why not run an H4 with stiffer spring in a carbine tube?

The goal is to slow down the BCG particularly when suppressed and the extra gasses are coming back towards the action, right?

I’m looking to really geek out on this topic for those with the info.

I’m working on a build but I’m torn. Carbine tubes and accessories seem more prevalent but A5s have me interested.