Not only is the NL giving more PA to younger players, its younger players tend to be better. Note that at the ages where the NL OPS is higher, it tends to be much higher than it is at the corresponding AL age. Where the AL OPS is higher, the gap is not quite as large. Even in the 31-34 group, the NL is better except at age 34.It's a good (and very detailed) article, so definitely check it out.
This bodes well for the Senior Circuit in the long term. Not only are their hitters producing at a higher rate, but their ages are in the range where we can still expect them to maintain or improve their performances. Meanwhile, AL teams keep signing older players such as Mike Lowell, Jorge Posada, Alex Rodriguez and Torii Hunter to long-term contracts. Over the next few seasons, we may see some AL clubs do what the Marlins, Diamondbacks and Rockies have done recently. Tearing teams down to watch young talent develop resulted in a high scoring National League, even without a designated hitter.
Also make sure to check out his blog, Baseball Musings. Some people have praised me for being prolific. Applesauce. I'm a dabbler compared to Pinto. It's just after 3PM as I'm writing this, and he has 15 posts up. He had 36 yesterday. This is not uncommon.