If your Marauder is dead stock, the best pellet is the 25.4 grainers. You can increase the diameter of the transfer port, and install a TSS, and get about 900 FPS out of the 34 grainers.
I've taken a couple of pigs with my .25 Marauder, but it is bottled and regulated. I can spit out the 34 grainers at almost 950 FPS, which is what it takes to do clean kills out to about 40 yards on pigs.