Other than the Mak platform itself (an affordable, tough little pistol), the days when 9x18 Mak held any advantages over .380 ACP for American defensive shooters are dwindling.
With the dissipation of Mak surplus sources, ball ammo in both calibers is now about the same -- indeed, .380 is generally cheaper.
More importantly, if you shoot factory ammo, the .380 has it all over 9x18 Mak when it comes to optimized hollowpoint options. The only surviving commercial Mak loads from major ammo companies that might be good expanding defense rounds are Hornady's (with XTP) and Cor-Bon makes a Mak Pow-R-Ball load.
EDIT TO ADD: Georgia Arms (a good smaller ammo maker) also advertises a 9x18 Mak load with Speer Gold Dots. However, there's some uncertainty about whether Speer has, or will, cut off the supply of Gold Dot bullets to Georgia Arms -- they have apparently cut off the supply to Black Hills. You'd have to ask Georgia Arms whether it's still available.
Contrast this with the huge range of high-quality, widely available defensive loads in .380 ACP -- Speer Gold Dot, Cor-Bon DPX [very promising], Cor-Bon [Sierra] JHP, Rem Golden Saber, etc., etc. You can drive to your local gun shop or big-box sporting goods store and expect to find a variety of good .380 ACP carry fodder. 9x18 Mak, not so much.
I'm talking commercial ammo here. If you handload your defense ammo, you can load Gold Dots for the 9x18 Makarov.
There's a school of thought holding that with these two smaller, blowback pistol cartridges, it's better to go with the increased penetration of full metal jacketed (FMJ) ammo and forego hollowpoint expansion altogether. If you subscribe to that school, then the slightly hotter 9x18 Mak round does retain a potential advantage. (And of course the Mak pistol has its own charms and strengths; worth acquiring for its own sake.)
But unless you handload defense ammo or carry FMJ, you might as well go with a .380 ACP from Bersa, CZ, or Beretta, or upgrade to 9mm Luger. Or so it seems to me.
