We'll I'm not saying one is better than the other, and once you get used to the 70 point system its quite easy. The trouble arises when people buy an MS graded British coin and try to sell it for UNC British prices listed in something like Spink. The MS graded coin may only be an EF by British standards so not worth the price they think it is.
Its an old saying but buy the coin and not the number on the slab. If you learn to grade coins (which does take a while, and different people's opinions of a grade of a coin can be different at times) then you can really know if the sellers asking price or the grade he assigns to a coin is right.
A lot sellers on online auctions over grade their coins, thats were buying from a reputable dealer also helps.