Re: your comparison, LWTs in Cassandra in 4.1 (about to release) offer global 1RT reads, and 2RT for writes. Your comparison suggests you take 3RTs? I suspect you may be moving to offering 1RT for those in the local region, and 2RT for all operations in another region?

You make a point of mentioning your MVs (and presumably your global secondary indexes) may get out of sync with the base table, which is the reason the Cassandra community decided to mark them experimental. The Cassandra community has become very conservative since it began being driven by users of the software. I should not draw any conclusions around the relative merits of features from this conservatism.

The Cassandra community paused feature development for several years, due to this very conservatism, in order to focus on delivering safety and reliability at scale. Now that's done, you can expect a lot more visible activity.