Ok so now we get down to the crux of it aye? It's not about speed, it's just about being a pain in the backside having to lug such a weight about. Perfectly understandable, but should have said so originally - like the teenager nervously asking the pharmacist for cough drops when really he wants condomsSeventy-thousand statement Mathematica financial models. I don't care if it's "fast" or "slow" (quantified in terms of brutal seconds between issuance and completion: modest number crunching session can last three or four hours on my current laptop), but I do desire it to remain "snappy" while it grinds away in the background. As a ballpark, if it handles moderately-hefty multimedia tasks suitably (such as light iMovie editing), you can be fairly sure it'll be reasonable while under heavy strain. While on the corporate network I can just offload the job to a cluster so it doesn't really matter, provided, as I stated, it remains non-frustrating.
I'm beyond doubt that the next refresh MBA will be slower than my current MBP (though I will opt for whatever SSD they have); my argument is that it will be more usable despite being slower because of the decreased annoyance of carrying it around.
If it's snappy interface you want, then the SSD will do the job. Buy a rev.B now and relax safe in the knowledge that the rev.C will almost certainly (99.9%) not look any different to the rev.B. Forget about black bezels and crap like that, and just enjoy the sensation of not having aching pain in your shoulder.