I'd get the 2014 if your budget and cashflow are limited.
If your cashflow is fine but you just don't want to overspend... 2015 might be a decent idea. The resale value is easily $100 or $200 higher per year, so while you can get a cheaper 2014, it won't necessarily end up costing you less in the end. It's also a bit more powerful. SSD is a lot faster iirc, like twice as fast. CPU is a small upgrade, not very significant. GPU is a very nice upgrade, nothing extreme but a solid bit of extra speed. And the memory got a small speed boost, too, which helps the GPU as it's on shared mem.
Overall, nothing necessary. I have Force Touch btw and don't use it because I don't use safari / quicktime for example. I think in a year or 2 you'll see so much 3rd party support that it begins to be a differentiator, but today it shouldn't be part of your buying consideration imo.
So if money was tight right now, I'd get the 2014 refurb. If money wasn't tight but I didn't want to throw away money, I'd get the 2015 probably because it's better and gets more resale value to compensate the higher price.
Also check out e.g. the Jetdrive 330 by Transcend. I think it's about $80 for 128gb, and you can save $40 over the next two months to save towards it. By the time you use up your 128gb, you'll be able to get another 128gb. Fact is, a word document or a movie simply doesn't have to be on an SSD, it makes zero difference. SSD is great for the OS, for video editing, for compiling or extracting archives etc. But you can probably get away with keeping a lot of your large files on an external SD card, or even an external drive. And you can get it as cheap as 8 cents or so per gigabyte for an external drive, all the way up to 80c per gigabyte for an SD card that sits flush with the Macbook and doesn't require you to lug around an external drive. And the speeds are fine for things like movies or music and light game files that mostly chill in memory rather than storage while playing. Exception are loading-screen heavy games that benefit from SSD. Compared to Apple's $1.50 a gigabyte prices, 8c is very interesting for tight budgets.
