Well, the advantages of pearl pistol is that you get it early at level 150. While powerful stinger is at 215.
I'm pretty sure a clean pearl pistol is more expensive than a clean 3s, bad base powerful stinger in any server. Your chances of finding a seller for a pearl pistol is greater than a stinger gun. Don't quote me on that though.
-Choose pearl pistol if you plan on reselling for some cash, have access to full pirate set, or want to OHKO at early levels.
-Choose powerful for a cheaper alternative long term wise and ultimate for a temporary poor man's replacement.
-Chaos tower guns are a good option too, if you've the time to farm them.