When it comes to buying bullion, everything has their pros and cons.
With generic silver (bars/rounds) you end up with a lower price per ounce (generally), you can get very convenient sizes (1/10 oz, 1/4 oz, 1/2 oz, 1 ounce, 5 ounce, etc.) but it comes at a cost of the next person not knowing for sure if your bars/rounds contain the stamped amount of silver. For example, would you (or an average person) know the difference between thick silver plated copper stamped .9999 silver and the genuine article? You've already got that problem with gold plated tungsten, (I know a lot of people laugh at the idea, but when you've got a Chinese firm openly selling these (see:
Tungsten Alloy-Gold plated Tungsten Alloy Bar ) you've got a (potential) problem on your hands). Even if you know for sure something is pure silver, how do you know that the person that you have to buy X off of when the dollar collapses will know that?
With junk silver (US/Canadian 90/80%) you've got a fairly low premium (depends on the dealer) a wide variety of sizes ranging anywhere from a dollar to dime and the biggest advantage is that its harder to -accurately- fake a coin than it is to accurately fake a bar (although there are some very good numismatic counterfeits, most of them are very good because they are made out of the metal, a gold coin would be made out of the same amount of gold, a silver coin the same amount of silver). The downside is that they aren't very easy to calculate compared to a troy ounce without a calculator and chart (or smartphone app!) handy.
With bullion (Eagles, Philharmonics, Maple Leafs, etc.) you've got a -high- premium that may or may not be recoverable. Today if you buy an Eagle with a premium there's enough demand that the shop will most likely pay you back at least some of the premium, perhaps not all of it, but they generally will pay you more for it than junk silver or a bar. However, if silver gets to be more expensive or the dollar collapses, there's no reason for them to pay a premium. Numismatically they will never be worth much at all due to their incredibly high mintages and the fact that only a handful have ever seen circulation.
A lot of people will say that the purer the better, while this is certainly true for coins less than 90% pure (40% silver Kennedies and 35% silver war nickels generally trade at a discount) I'm not sure that this will be true for this silver market since much of the demand is from investors rather than industry. When we saw high silver prices back in the late 1970s, the demand was almost entirely industrial (except from the Hunt Brothers), the jewellery makers such as Tiffany had a supply crisis, they couldn't get enough pure silver to get what they needed to make their jewellery because it was all going to the Hunt Brothers, because of such a massive sell off of silver, refiners were packed and it took a long time to get things refined. In 2013 this is not the case, a coin shop can just as easily sell back the 90% silver that you gave them to another investor, there's no need for them to melt it and refine it (and take a loss).
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