I have a choice of flying on AA or Lan to Lima from NYC.
Which of these two airlines' BC is better, in terms of seats, entertainment, food, and overall service/attention?

Succinctly, and without a doubt, LAN!

Can you explain why? and is there a difference between Lan Peru and Lan Chile with regards to the aboved mentioned?

LAN Per� is basically LAN Chile with a few personnel changes; JFK-LIM nonstop service is LAN Chile, LAN Per� codeshare, according to OAG. But the service (incouding beverages and food) are superior to American's, especially when you consider AA flies one-stop (via MIA) AB300-600s to LIM, LAN is flying nonstop B767-300s. In my experience, LAN has more comfortable cabins, plane for plane, but the AAirbus is a lot more - antiquated?

A search on AA and Other North & South America Frequent Flyer Programs fora will reveal recent experiences on LAN. (N.B. LAN Ecuador and LAN Argentina, at leasit in part due to the governmental limitations on foreign airline ownership and investment, and therefore operational control, are not oneworld airlines... LA and LP are.)

On the return, you would have to disembark and process US Department of Homeland Security (U.S. Citizenship and Immigration Services and US Customs & Border Protection) in MIA, process back airside and... just from the logistical point of view, forget it!

Lan. The business seats have generous recline and pitch. The 767 will most likely not have AVOD (they only have a few with this), but still a PTV with several movie/tv/map selections. The wine selection is generous, and good. Food is good to very good. You won't be bombarded with announcements. Curtains don't pose a threat to anyone's national security, and the cabins provide for a somewhat restful snooze. You never hear the FAs pissing and moaning about work conditions, although they work harder than any US carrier. I like the accent of chilenas speaking ingles.

Are flights from Lan more on time with regards to departure/arrival in comparison to AA flights?
What's the seat configuration of Lan's BC?

I believe there are 6 rows of 2-2-2 (although one row may not be a full row?)

On time - I have flown Lan on approx 6 RTs to/from the US, within South America a few times, and within Chile on many flights, and I had 2 sizeable delays, total. One was a late arriving aircraft to LAX (2 hour delay), and the other was a fire near SCL shutting down ops due to the smoke (similar delay). Any other delay that I've had was unremarkable. I did notice a couple of longer delays on other flights while at SCL last week.