[ivansanchez]

Leaflet maintainer here. AFAIK, Leaflet still has a nicer learning curve compared to OpenLayers (which doesn't affect long-term OL users like you, obviously), and a plugin ecosystem which allows for smaller library size.

The OL3 folks have been working hard on making OL3 leaner (see the "Faster, smaller, better" talk from FOSS4G Bonn here: http://video.foss4g.org/foss4g2016/videos/index.html), but I feel Leaflet still has an edge on that regard.

Also, OL3 depended on the Closure compiler for a long time, which made it difficult to interoperate with other frameworks, which is why a lot of React/Ractive/R/Django/Vue users choose Leaflet.

Other than that, there's no clear obvious advantage of a library over the other one. We have a friendly relationship with the OL3 folks, we try to copy some of their features, they try to copy some of ours, everything gets better in the end.