I would like to point out that no one should be in favor of Al Jefferson, and not in favor of Lopez.
They are both among the best offensive big men in the game, but are flawed otherwise. Jefferson is a better rebounder, but horrendous defender, Lopez can defend a bit, but is not a good rebounder. They are essentially the same players, except Lopez is younger, bigger, and until this season, less injury prone.
The "terrible rebounder despite being 7 feet" thing bothers me a heck of a lot more than the fact that Big Al is a bad defender. I think if you pair Big Al with the right kind of athletic defensive 4 you wouldn't have such a bad interior defense.
Lopez's poor rebounding, on the other hand, speaks to a bigger issue with him as a player, since he should have the physical tools to rebound passably well, and yet doesn't.
I don't really get your logic here, you can pair Lopez with a stronger rebounding 4 the same way you can help Big Al with a more mobile defensive 4.
I guess my point is that Big Al seems to do the most with the tools he has -- Lopez does not. That's not a good sign.
A bad sign is going through as much of his career as Jefferson has, and never really making a team better, despite the numbers.
I am by no means making a case for Lopez here. While I think there is still a lot of potential there, he will cost way too much on the open market to take a flyer on him.
But, the point is, they are essentially one in the same. Players who put up the stats, but aren't winners. They are both immensely talented (and no, Jefferson is not doing the best he can with what he has...if Big Baby can be a passable defender, Jefferson can be an excellent one), but are missing that little extra it takes to be driven to be the best basketball player they can be.
While either of them could be quality pieces to a winning team if you put the right guys around them, they are likely to never be the players that their potential shows they could be.
Honestly, the only real significant difference I see between them is that one of them used to play for the Celtics, and the other didn't.