Playing the Japanese settlement on Beta, and find it a bit faster paced than Vikings. It seems to have a little more flexibility in designing the city (e.g the torii gates can be placed either 1x3 or 3x1), The addition of the Merchant makes it more interesting as well, as it can provide a way to buy expansions earlier on. There seem to be more impediments, however, so the city layout is more challenging, which also provides more opportunity to be strategic in how and when you place buildings.
Since you can do both (but not at same time) alternating between Vikings and Japan can break up the tedium a bit compared to doing 15 Viking settlements in a row.
But.....I'm not as enthused about the Shinto Temple, compared to the Yggdrasil , since the lvl 10 Yggy has that great 30% attack boost. Shinto replaces it with a supply boost, which isn't as useful to my needs. Of course, others might find that great; it just doesn’t work for me.
The 2nd building, the Timeless Dojo, is also less interesting (IMHO) than the Viking’s Runestone. I'm using the Runes to replace some SoKs.