13 air or 13 pro retina (certain specifications and needs)

[life4567]

Hi, I want to buy a macbook, and I am not sure whether to buy rmbp 13 or air.
my use will be web browsing, word documents/powerpoint, downloading lectures from the internet, iTunes library, as well as a few other apps.
I will either buy 8gb ram, 256 gb ssd air.
or 8 gb ram 128 gb ssd pro.
I want the processor to be fast enough to last 3-4 years, without being slow (in 2-3 years). So is the air processor good now and future wise? Or should I go for the smaller ssd, but better processor in the rmbp 13. Before u say get 15 retina, I am not considering the 15 inch retina at all
Thanks

[Macman45]

Judging form your use, I'd say the Air would be a good bet for you. It will easily do what you require of it, and I'm still happily using my 15 month old 17 Ultimate for even more intensive stuff...