I have had a few Slabbed coins in the past, I' am sort of old time when it comes to these. I feel that the "Good" points of haveing a coin graded is when you have a rare type of (Die Variant), or a 1922 p lincoln, 55 double die ect...or to authenticate a type coin. I do believe this will add some value premium to the coin rather than being in raw state.
On the other hand I have experienced Dealers who will push this as explained when they sell you these coins, but when you go to sell the same "Slabbed" variant coins, they wont give you the premium of being slabbed! they will just gray sheet you regardless (Wholesale), but will most absolutely charge you for the same coin slabbed when it's back for sale in their shop!.
So....The other helpfull advice for slabed coins is that it does take alot of the gradeing questions away from the dealers who otherwise would really "DOWN GRADE" your other wise "RAW" coins!.Yes, very few graded coins I will disagree with the grade, but all in all the coin has been checked-out by the pro's, so when I do sell my "Slabbed" graded variant coins to a dealer in the future, you bet if he wants it, he will pay me for it!!!!!!!Thats why dealers love it when you bring "RAW" coins in for sale, and hate it when you bring in "Slabbed" coins, because they know their chance for "DOWN GRADE" has been taken away but will still try and give you a wholesale "RAW" coin price.
I love Raw coins and will still keep them that way, only exception is the rarer types mentioned. Happy collecting!!