Non-corrosive primers were originally highly unstable, which is why the U.S. stuck to corrosive primed through WWII. The US was especially concerned because heat destroyed the early NC primers and we had troops in tropical areas even before the war, Panama for example. Having several billions of rounds of ammo go dead in the middle of a war would be somewhat embarrassing, to say the least.
After new NC formulas proved stable, almost all countries and manufacturers went to NC. Most of the surplus ammo being sold is from WWII or just post WWII and is corrosive. Some more recent (1994?) may be corrosive, but I doubt it; some sellers have advised treating it as corrosive simply to protect themselves.
Yes, cleaning is not that difficult. But I have been there, done that, don't want to do it again if it can be avoided.
Jim