Dropbox seems to be growing faster (maybe mattermark knows for sure), and I think Dropbox intentionally hires technically-overqualified people (like Google and Facebook did) as a way to attract other competent people. My perception, which may not be accurate, is that Twitter doesn't do that. From the Twitter employees I've spoken to, it's also not a place people who could otherwise work at Facebook or early-Google would want to work -- it got late-Google political before becoming wildly profitable.
It went from really shitty infrastructure to somewhat less so to somewhat less so, vs. starting from crap and doing amazing work to make it work well (Facebook), or technical excellence from day one (Google).
OTOH, Twitter is way "cooler" than Dropbox, in terms of having political impact, standing up for users vs. the US Government, used by "cool" (non-tech) people, etc.
When you're in such a situation, a lot of people don't realize how strange and self-involved it sounds to say things like that.
To me, it feels like "We have the best people! You don't work here, so you must not be very good. Therefore, I'm better than you."
That's obviously not what they mean, but it strikes chords of jealousy and social exclusion when shouted in a public square.
Twitter has always been known for their Super Ego Employees though. Work 12 hours a day, go home, run twelve miles, cook a gourmet dinner, have three dates (sleep with two of them), check email before bed, sleep for four hours, then start over the next day. (with oversharing online humblebrags every step of the way, obviously)
I don't know much about Twitter internally but from the outside they seem to have a pretty impressive stack. I personally love their Scala, Storm, Bootstrap, Twmemproxy, Cascading work.
If you're joining the company today, there better be significant growth story to justify 4x-5x growth from $10 bil baseline. If it's just 2x-3x, heck, joining GOOG, YHOO or AAPL might yield the same results if you timed it right.
