Exciting update! How does the new vector tile system handle performance on low-end devices with large datasets?

... it doesn't?

One of the downsides of MVTs and the typical max zoom level of 14 is that that they do require more local resources than simply rendering a 256x256 bitmap.

For OSM the question is naturally would a complete migration (aka turning off raster tile support) exclude any noticeable number of people from contributing.

But right now that decision is still a long way off, the vector tile service hasn't even been integrated in osm.org yet.