2012 MacBook Pro 13 or 2015 MacBook Pro 13 with Retina Display

I am looking to buy a MacBook Pro 13 inches, and Best Buy (Sacramento, CA) has a deal for 2012 MacBook Pros. I am wondering which to buy.

What I use it for: scholarly research, web browsing, itunes, watch videos on Netflix and online. There is no graphic/art or gaming needs. I also don't download any app unless I need them and I can't get them on my phone.

What I hope to have: fairly good battery (7 hours for 2012 seems to be good enough), fairly fast system (old pc was 2.27GHz and I was fairly satisfied), storage as large as possible, and the expectation that I can still use it as long as possible. I know MacBook Pros are legendary for quality and long lasting, but better RAM and processor may mean it can run "normal" longer.

Specs for the MacBooks:

2012 MacBook Pro:

Intel Core i5 Processor, Intel HD 4000 Graphics, 5400 rpm SATA hard drive, up to 7 hours of battery life, 802.11 n wi-fi, multi-touch trackpads.

Processor speed 2.5 GHz, Memory 4GB, Storage 500 GB.

2015 MacBook Pro with Retina Display, 256 GB:

Intel Core i5 Processor, Intel Iris Graphics 6100, Flash storage, up to 10 hours of battery life, 802.11 ac wi-fi, force touch trackpad.

Processor speed 2.7GHz, Memory 8GB, Storage 256GB

(The heavier weight doesn't bother me)

NOTE:

Please also consider that, with a much larger storage in the previous model, the MacBook speed gap is a bit less than what the specs may suggest, and the question is, does the 4GB extra Memory and 0.2 extra GHz still make a significant difference even if the older model has 244GB more storage space?