"This database is good at high concurrency writes" and "this database has very good write performance" strongly favors MongoDB.

This is interesting because MongoDB has taken a lot of flak for their global write lock. Also, updating a MongoDB document can require moving it if it grew too much for it's allocated space, which is another thing that hurts write performance. I guess these things haven't hurt their public perception of their write speed as much as I thought.

You have to remember that this is relative to SQLite, which has a global write lock of its own.