Will a 1.8GHz MacBook Air be much faster than a 1.3GHz model? I am looking to purchase a refurbished Macbook Air from Apple's refurbished store. 

When comparing the models there are two I am looking at. The difference between the two is slight but one of the difference is the processor. 

One has a processor of 1.8GHz dual-core Intel Core i5 (Turbo Boost up to 2.8GHz) while the other has a 1.3GHz dual-core Intel Core i5 (Turbo Boost up to 2.6GHz).

I am experienced with PCs but not Macs. The price is nearly identical ($20 dollar difference.)

The newer model is 1.3Ghz.

Am I going to see a big difference in speed between the two Macs?
1.3 GHz seems to be mid-2013 Haswell based machine with Intel HD 5000 graphics, the other one is probably mid-2012 Ivy-bridge one with Intel HD 4000.


Haswell based CPU is about 5-10% faster than Ivy Bridge according to various benchmarks (so, all in all it should be comparable in terms of pure speed, but read further)
Haswell chips make SSD drives run faster
Intel HD 5000 is much better than 4000 (and that will give most significant boost to overall performance IMHO)


So, if all other specs are the same, I'd go for 1.3 Haswell one, the problem is that you never know what you'll get when buying refurbished machine.