I like to have my coins graded for several reasons: 1) NGC guarantees the authenticity of your coin. If you determine in the future that the coin inside an authentic NGC holder is fake, NGC has a guarantee to compensate you. 2) You get more protection if you decide to sell your coin online because the serial number makes it easier to identify compared to a raw coin (in case the buyer wants to return the coin or says that it is not as described). 3) Coins in OMP usually move around a lot. That makes me uneasy because the coin can be damaged over the long run. 4) Although slabs are not a perfect seal, I think it's a lot better compared to the seal of the OMP. 5) NGC's holder is similar to the holders used by the Smithsonian to house its most valuable coins. This gives me more confidence with NGC's long term preservation prospects. There, you have five good reasons to send your coins to NGC for grading!