Either is fine as long as pay based on the silver content for them. Don't pay anything extra because it is a coin.
You can't be sure any coin is a true collector coin. Many are freshly minted and have no extra value other than their silver content.
Either is fine, just don't overpay. Remember you buy at a premium, and you sell at a discount. That's why physical silver is mostly a bad investment.
By the way, I collect Morgan silver dollars.
whichever way lets you buy the silver by weight is fine.
if you get coins it's possible you might be paying more than what the silver content is worth, for "collector's items"
but lots of coins are sold for the weight of their silver content too
just make sure you know what you're buying
Candy bars, more like it. Don't speculate on commodities.