General silencer discussion. If you want to talk about a specific silenced rifle or pistol, it is best to do that in the rifle or pistol section for that brand.
I have not heard the difference, but I have heard a XL on a 10.5" ar15 9mm, and it was very quiet (I ordered one for a customer). It was very similar in sound to a MK9K. Nice can. I would go with the XL.
The Cobra has a LCD built in so you can use it on Browning style pistols as well, if thats a consideration. You would need to use the fixed barrel spacer on the AR. The XL should be longer but quieter. The Wraith would be comparable to the Cobra but minus the LCD.