Advice Needed - What's more important: Number of cores, RAM, Processor? Comparing similarly priced Macbook Pro's from 2012 - 2013

Question

What is more important? Cores, RAM, Processors etc?
There are several models available right now on the apple store that are similarly priced but offer different specs.
I'm looking to purchase a secondary Mac for making music (house/techno in Logic) on the move and to be able to carry out basic work tasks.
The models at similar prices available are:
Refurbished 13.3-inch MacBook Pro 2.9GHz Dual-core Intel i7      
Originally released June 2012
13.3-inch (diagonal) LED-backlit glossy widescreen display, 1280-by-800 resolution
8GB (2 x 4GB) of 1600MHz DDR3 SDRAM
750GB Serial ATA @ 5400 rpm
8x double-layer SuperDrive (DVD±R DL/DVD±RW/CD-RW)
Intel HD Graphics 400
Refurbished 15.4-inch MacBook Pro 2.3GHz Quad-core Intel i7
Originally released June 2012
    15.4-inch (diagonal) LED-backlit glossy widescreen display, 1440-by-900 resolution

    4GB (2 x 2GB) of 1600MHz DDR3 SDRAM
    500GB Serial ATA @ 5400 rpm
    8x double-layer SuperDrive (DVD±R DL/DVD±RW/CD-RW)
    NVIDIA GeForce GT 650M with 512MB of GDDR5 memory
Macbook Pro 13-inch: 2.4GHz with Retina display Dual-core Intel i5
2.4GHz dual-core Intel Core i5
Turbo Boost up to 2.9GHz
8GB 1600MHz memory
256GB PCIe-based flash storage1
Intel Iris Graphics
Built-in battery (9 hours)2
Which should I go for? Is retina all together a better machine and a good enough update, or should i go for a 2012 model which is almost maxed out like 15.4?
Any advice and experience of these machines is appreciated.
Thanks,
kkd_ldn

Answer 1

kkd_ldn,
because the RAM in the Retina models is non-upgradeable, I’d say that RAM is most important on the Retina models.
All of the models above will perform basic work tasks well; I haven’t tried making music on my Mac, so I don’t know what the bottleneck there might be. If it’s CPU-intensive, then the 15-inch quad-core model might be the best choice, despite its slower CPU speed. You can upgrade the RAM on the non-Retina models if RAM turns out to be a bottleneck.