Is Asian Buddhism versus Western Buddhism a fair comparison? Honestly, it’s like comparing characteristics of America to the Perth metropolitan area. There is a real issue of scale here.
Not to mention that the timescales aren’t exactly comparable, either. When self-styled Western Buddhists are writing about “Asian Buddhism,” it’s never entirely clear to me if they’re writing about something they saw the other day or read about in a historical text written by some clueless white guy European colonialist.
Buddhism in Asia is greater, more diverse and far, far older than Buddhism in the West. It will continue that way for the entire span of your natural life. When writers like David Nichtern attempt to describe Buddhism in Asia, they end up as nothing more than blind men feeling about an elephant. Their arguments create a fictional Asian Buddhism to use as a straw man in order to define their vision of a separate Western Buddhism. This rhetoric is colonialist at its root, and I encourage them to do better. I have no doubt that they could.
Update: In response to some thoughtful commentary below, I had to put it in print: sometimes I get it wrong.