It kinda depends on the neck wall tension of the sized or not sized cases and the bullet dia. Im working with. What you want for field/hunting ammo may be a tighter fit than what you would just shoot targets with, too. In general, the snug fit I like for cast bullets wont just fall or easily pull apart, though this wonderful alignment of the planets does not always happen right away. What I do not want to do is mess up a nice cast bullet that fits the throat well by forcing a crimp on it that it will then have to scrape all the way on out of. On jacketed you do not want to crimp if there is not a cannalure or such and the resizing dies are supposed to undersize the neck enough to give very good neck tension on the smooth sides of the recommended bullet diameter.
IMHO, if you cant easily push a bullet deeper or pull it out of the case there is NO need for a crimp, except with certain powders that tend to burn better with high launch pressures.