Depends on what you want and the way you expect things to go in the future.
Myself, I trade in a good chunk of 40%ers and lower-quality 90%ers for collectible coins, usually Britannias or other British silver, or foreign coins. The reason why I do this is if silver falls, you still have a coin worth value (remember that Britannias have a maximum mintage of 100K coins) back when silver was still $12 an ounce or less, Britannias were still trading at $30-40 a coin. Of course if silver shoots up to $50 an ounce, you'd be better off with coins with less of a premium.
90% US coins are a good bet, but if silver prices fall, they fall too. Some still have a higher premium than generic .999 rounds/bars but have the advantage of being very recognizable (nearly everyone knows that they are silver).
.999 rounds have the advantage of being easy to get rid of if we see a panic like we did during the Hunt Brothers time (long lines at the smelters to melt down coin silver because the demand was for pure silver) but are hard to convince people of in a SHTF scenario, its easy to see this quarter looks like a quarter, but how do I know you didn't just silver plate a chunk of copper and stamp .999 AG on it?
There is no, excuse the pun, silver bullet when it comes to trading up, everything as advantages along with disadvantages.