Hi! To avoid having too long loading time, we have the support for incremental loading. But we definitely need to work on optimizing the size of our scene format also.
We have great things coming on babylon.js in the next days. It's mainly a personal project we have as a small team with David Catuhe, Michel Rousseau and Pierre Lagarde. We have great feedbacks so far!
demos look quite nice but wow they take a long time to load, took about 5 minutes to download 50mb for a short scene, makes me wonder if download times are going to be a limiting factor in webgl games.