The difference in a practical sense is that ML pitchers can take a hitter's weakness and turn it into an 0-30 in the blink of an eye. You just do not see the steady stream of good to excellent pitching at the AA level that you do in the ML's. You see more polished pitchers in AAA but they are not up to a ML standard either and that is the problem, particularly in a year when you are trying to make a run.
Look at what has just happened to the Sox themselves, a team full of ML class everyday players. Stick a few pitchers in a row that are all in the upper half of the league's pitchers and what do ya' get....what 4 runs in 29 innings up till last night. That is my general comment about hitting in AA vs the ML's.
As for the specifics regarding XB;
What the Sox need out of a 3rd baseman is standard league average defense attached to a bat with some real pop and with the lack of HR pop in their lineup that means HR power.
XB has got 6 HR in 219 AB's in Portland this year. He has got a nice collection of doubles and some triples. So his slugging %'s are pretty good in spite of the lack of HR pop. However I don't see how that makes him the equivalent at this stage of WMB if WMB comes back right. WMB has 6 HR's in 81 AB's at Pawtucket while struggling to regain his confidence and changing his approach at the plate. The longer WMB goes at Pawtucket the more I think what we really see is him back in a Sox uni after the ASB.
If WMB still cannot lay off that low and outside slider, the one that is usually heading lower and farther outside, then there is no sense in seeing him back here. Others suggest that WMB must learn to take that pitch the other way. Good luck with that one. I think WMB is past saving in that regard and even if I am wrong, that is a shift that would likely take an offseason to realize at least relative to ML pitching. Before WMB was sent down even the balls he was hitting to RF and RCF were not efforts to go that way and if you would look at slow-mo of his swing at that time, you would easily see why. WMB "says" he is doing better now cause he is getting ahead in counts and getting more FB's to hit. Well in fact the only way to do that would be to lay off that s*** that he refused to lay off of. So, maybe I have the answer to my own question.
Finally, if we were to bring XB here, where do you think he would bat....8th, maybe 9th??? Do we really need another 8 or 9 hitter up here?