2013 (or '14) MBA vs Early 2011 MB Pro

Absolutely not. First of all, Apple won't service that thing even if within warranty due to the dual SSDs. That is considered changing a non customer installable part. Second of all. You can get a MacBook Pro 13" Non-Retina for $1199 and add a SSD and 16GB of RAM for under $200 more. Or even buy a Retina for $1299, albeit with less RAM and storage.

Personally, I find that I take great care of my Apple products and I hate it when they get even a scratch, let alone a dent. So, once you own it you will regret it. Stay away from this one, the lack of service from Apple, expensive price for what it is, and condition all make it a lackluster deal.

Altemose

I'm not going to comment on the price. Without the upgrades it would be too high. Saying 2 ssds is meaningless though. It doesn't mention the capacity or condition of those ssds or even whether they remain under warranty. I would place little value on any out of warranty drive, including an ssd. That includes those used by Apple. People have actually reported mixed results when it comes to obtaining out of warranty service on dented machines or those where the optical drive has been replaced with an ssd. For predictable service responses, I would want to restore the optical drive if you require service. It's upgraded ram, and that ram was probably never tested. If you buy it and experience problems, check the ram first. The 6750m isn't going to be that great for the latest games, but assuming it's in good condition, it would handle the other tasks.

What I do question is the comparison between an Air and that one. There is still a significant performance gap there if you stress the two machines. I'm not sure about the Air, but I know that early 2011 may get uncomfortably warm if you're really using it. It may not be fun to use it in a chair if it rests on your lap.