Re: Better platform for a can - 9mm or 45acp?
If by "easier to suppress" you mean what will be easier to make the quietest than 9mm is the answer. The TiRant 45 and Osprey 45 suppressors are the BEST .45 ACP suppressors you can buy and don't need to be shot with wet medium in the suppressor to have good sound reduction. But even with these suppressors a .45 host is slightly louder than a 9mm host with quality suppressor.
Just because 45 ammo is subsonic does NOT mean it is starting from a point conducive to being very quiet with a suppressor! The problem with the 45 is the larger diameter. You have a huge hole in the end of the suppressor and a lot of sound typically escapes through this.
Until the Osprey and TiRant products, all quality .45 suppressors (with very few exceptions) needed to be shot "wet" with a medium like wire pulling gel to get close to sound reduction of a quality 9mm suppressor.
Bottom line, the 9mm is "easier" to suppress. And 147-grain or other subsonic ammo isn't hard to find at all. At least I've never had a problem in all the years I've been shooting suppressed 9mm hosts.