They make you super cool
Depends on the cartridge. 243 AI is a laser, but at the cost of 1000 round barrel life. 280AI will land just shy of 7mm rem mag velocity. Again, uses more powder and barrel life than the standard 280.
In my 243 I'm burning 46grns of h1000 behind a 112 match burner to push them right around 3000. Guys are pushing the 108s to 33-3400, but it gets harder on brass and barrels.
The 6mm brx is only 2-300 fps slower with 10 grns less powder and a 3000+ round barrel life.
Some things are just fun, like a 250 Savage AI. Bump up the velocity a ton, but it's not as special now that 25 creed is easy enough.