1248 cards in the game are MLB Live cards so it often seems like there are a lot more live cards in the game. On top of that, the odds of pulling a live card is higher compared to historical cards, hence the Auction house tends to have lots of Live cards.
In theory, a 79 is a 79, no matter what type of card.
However, here comes the tricky part. The rating is more a general rating and it is more important to look closely at the various ratings. As you move up in the leagues, you tend to encounter nothing but superstar players that can easily make contact and hit home runs. In this regard, you want to find pitchers that prevent automatic scoring via HRs.
As a result, a 86 Dallas Keuchel card may end up as a top15 card and be better than many of the 90-99 diamond cards.
So in this regard, a 86 card can perform like a high 90s card. This is because his movement rating is 96.
There are many other examples in the game like this (78 Barker, 78 Ozzie Smith, ….). These cards have stats that tend to perform well in the game and fit many of the teams that people try to build (strong defense at SS, high movement for pitchers, good contact for batters, …)
Given the fact that the game features almost all the superstars of the last few decades, you tend to see more and more historical cards among the top teams in the PT universe.
There are a few discussion topics on what players tend to perform well:
http://www.ootpdevelopments.com/boar...d.php?t=297821