Which processor for future-proofing?

Get the 13 inch it doesn't sound like you need a quad core and unless you suddenly change your habits and what apps you use you won't need a quad core for the forseeable future. RAM also makes no difference unless your workload or apps need it. You can't future proof a computer, not really, the ranges of chips are much the same for each product line and are not going to make the computer last any longer. Will the 15 inch be able to run more demanding software faster??? Yes of course but if you don't use that software then it's not a lot of use.

 

There are always no processors being released with new features.

The problem is that if Apple releases a laptop with a new processor say in August 2015, developers cannot take advantage of these new features immediately - because almost no Macintosh could use them! So for about four years, having that new processor doesn't actually give you any advantage. (If it's faster, or uses less power, that's obviously nice, but not because it is a newer processor).

So as a developer, I'd want everyone to switch to new processors as quickly as possible, so that I can take advantage of new features as soon as possible. But as the end user, any newer processor is equally fine for many years to come. So given the choice between an older quad core and a newer dual core, I would always go for the quad core. Obviously taking into account the cost.

 

More important to take into account the use, if nothing you use makes good use of the quadcore it really isn't worth going for.

 

Similar situation to myself but I also do some iOS Development, iBook Publishing and Revit using Parallels.

I went with the Retina 13, 2.9Ghz Dual Core, 16GB RAM and 512GB SSD. It flies. Does everything I'd want from a laptop and while running iTunes on Mac as well as Parallels with Windows 7 open running Revit, I still get above 5 hours battery.

Encoding video is slower than the quad core by 50%, but I don't encode, I make sure all the video files I download are MP4, which seems to be the most common format now anyway.

 

I wouldn't worry too much about the processor since they changed the focus from power to efficiency, it's now more a case of picking a size that suits & best graphics card you can get, as going forward that's likely to be the limiting factor.