Gay and Aldridge are both down, stat wise, by similar amounts this season, but Aldridge is still ahead of Gay in both EFF and PER.
Aldridge:
2007-08 - PER = 18.5 EFF = 18.46
2008-09 - PER = 17.9 EFF = 16.85
Gay:
2007-08 - PER = 17.5 EFF = 18.42
2008-09 - PER = 16.9 EFF = 16.12
Gay scores more, but Aldridge remains a slightly more productive, slightly more efficient player. Disregarding positional need, I think if the 2006 draft redone today, most GMs would take the big man (Aldridge) over the higher scoring, but less efficient wing (Gay). Their performance is similar enough that the deciding factor would be their size/position and that tips the balance in Aldridge's favor.
I also think both players' slightly decreased performance this year can be attributed to changing roles and adjusting to new teammates.
BNM