Yep, I went back and fourth time and time again on this very issue. I ended up going for the 128Gb W/ 8Gb RAM. The RAM was something that was holding me back from Air originally, so the extra $100 for the upgrade isn't part of the $300 for the 256Gb version.
For me I'm going the other way and getting away form big 1Tb+ spinners. I know it's small and not cheap, but an external 128Gb SSD is the same money as the upgrade, doesn't require a power cord, small enough {0.4"h x 2.7"w x 4.35"l}, and I would have to believe more secure than a traditional hard drive.
I don't play games, I don't down load movies, everything I have seen in the Mac OS is more than able to perform my tasks of photo editing and video editing. I'm also moving away from holding on to stuff that is not going to be used. Photos are a great example. I have so many bunk photos on my PC. What for? I only use the crops. The rest are junk files taking up space. Just like raw video. Hours and hours that I might never look at again after I make the first video clip and post to youtube.
New way of thinking for me. Load it, work it, save the finished project to external, and dump the rest.