It is difficult in trying to sort all that out. Myself, I have a mid 2013 13" MacBook Air. It has a 1.3 GHx Intel Core Processor and 4 gig of Ram. But, the machine is rather "snappy", as it has a TurboBoost feature, and a 256 Gig SSD (Solid State Drive). And, of course, I keep the machine in tip top shape regarding disk maintenance/repairs, software updates, backups, continually cleaning off unnecessary stuff, etc.
I also have a late 2012 Mac Mini. It has a 2.3 GHz Intel Core I7 processor, 4 gig of Ram, and it came with a (slow) 1 TB 5400 rpm hard drive. But, that 5400 speed is s "drag", and after I replaced that drive with a fast 256 Gig Samsung 840 Pro SSD, it is much, much faster. (I also keep the Mini running "mean and clean").
So, I guess you need to see how much "need for speed" you require. I would definitely go with an SSD, as that makes a world of difference. Also, if you either need to run quite a few applications at the same time, or run ones that need a lot of memory, then you'll need at least 8 Gig of Ram. Myself, and for my processing needs, 4 gig is enough. As it is, I can only upgrade the Ram in the Mac Mini, so with the newer laptops from Apple (I believe all of them, but definitely the MacBook Air), once you purchase it, you cannot upgrade the Ram at all.
