Need help on deciding which caliber Marauder to buy

So my current air gun is a Ruger Blackhawk elite .177cal. (For all intensive purposes, let's say it's a RWS Diana 34, cheap clone) With that being said, I have been able to squeeze impressive accuracy out of this cheap Springer using heavy pellets and a few other upgrades to optics and mounts. But it leaves me wanting more out of it than it could ever do... that being said, I'm in the market for a Marauder, but I can't decide on what caliber. Most important to me is accuracy/killing power out to 75 yards or more. Second most important is noise, will either of these guns be as loud or louder than my break barrel? My dad has a .22 mrod and it is definitely quieter than my ruger. How much louder would a .25 be? Looking to buy within the next two weeks. Any and all input would be appreciated. Thanks.
 
At 75 yards .25 or larger is your best choice. I have 2 (One is an Armada) and even though I have several high end PCP's the Marauder in a Bull Pup aftermarket stock is my go to gun most of the time. I have taken coyotes, badger, skunk, armadillo, cottontail, and a plethora of grackles. I am running a different spring that stock but everything else is basically factory settings. .25 and .22 marauder were little different in volume to my ears but you can always add an aftermarket adapter and a suppressor to the end of the shroud to really make it whisper quite.

Thurmond 
 
So, it's looking like the .25 is the most popular recommendation. I'm not worried about pellet availability, when I order ammo I always do the buy 4 get 1 free deal, so when I get to the last tin I'll know to order more. Any other drawbacks to the .25, other than 8 shot instead of 10 and less shots per fill? Like I stated before my main concerns is accuracy and noise level.
 
First of all, .25 caliber pellets are sold by everybody. I buy mine at Pyramyd Air, and have never waited. There was a shortage of JWS a few months about a year ago, but that is well behind us.

I have a bottle, regulator, .162 transfer port, and TSS on my Marauder. It shoots 25.4 grain AirArms at 910 FPS, and the 75 yard groups hold better than I can (about quarter size in dead wind).

If I have a complaint, it is the hardness of the pellets. Though they do kill cleanly most of the time, center shot pigeons often fly away, only to drop out of the air a bit later. 

Oh, you ask about the number of shots. The regulator is set at 2,400 PSI. The .36 L bottle is aired up to 3,200 PSI, and down to 2,500 PSI. I get 14 shots.
 
wasn't saying there was a shortage Alan just that you cant hardly buy them but from actual an airgun dealer .177 and .22 you can find just about anywhere but .25 and up and you have to buy online.

Yote I wish me and Thurmond had recorded our pond shooting we were popping turtle heads outwards of 75yards in high winds

Jay to be honest I come from the Big Bore side of the hobby so having a gun that shoots more than 5 full power shots is a rare thing for me.
My Mrod is tuned hot with a lot of spring pressure and I still get at least two clips per fill.

I shoot the H&N Hunters Extreme and love em 
 
Another vote for the .25 Mrod. I was scared off of the .22 because of reported accuracy problems and didn't want to play the "barrel lottery". I have mine tuned down and get 32 shots (4 mags) of consistent accurate shots on a fill from roughly 2900 to 1800psi. I don't remember exactly but I believe that's at about 33/34fpe. That's with either the JSB 25.39 or Air Arms 25.4 at about 40 to 45 yards.

Ed