So there are actually a number of differences between Adam Moore and Rob Johnson. Johnson, for example, has a better idea of the strike zone. Moore was born in Texas, while Johnson was born in Montana. Moore doesn't make us want to slam our throats in a car door, while Johnson makes us want to slam our throats in a car door. The title of this post is very misleading.
Still, in keeping with the point, I'd like to mention that Adam Moore's home run off Dallas Braden yesterday had a measured distance of 441 feet, making it the third-longest Mariner home run of the season.
We've heard from some scouts that Moore has surprising power, and while that has yet to translate with any consistency to the Major Leagues, last night was one example. He's a strong guy, and he can hit with impressive pop when he pulls the ball to left field. That's something you can't really say about Johnson, and the difference becomes apparent when you look at how they've done against upper-level competition (AA, AAA, bigs):
Moore: 12.0 plate appearances per extra-base hit, 38.2 PA/homer
Johnson: 14.4 plate appearances per extra-base hit, 75.9 PA/homer
Neither of these two guys is hot stuff when it comes to blocking the ball. They both have decent arms. Johnson has slightly better plate discipline, and makes more contact, while being only a ~year older. Based on those things, you'd think Johnson's the better bet going forward. But Moore has the stronger bat - by a considerable margin - and it's that ability to hit the ball a long way every so often that makes him the more interesting player, with more interesting upside.
Rob Johnson is a known entity. Rob Johnson is what he is, and he doesn't have much further to develop. Adam Moore has promise. He flails a lot, and he misses a lot, but as frustrating as that can be to watch, try to remember that you're not just watching a taller, hackier version of the other guy that nobody likes. Moore's a different player, and if he can hit for the power he's shown himself to have, he'll be a better one.