I don't know. I don't even really know how my favorites are classified. People say Aes Dana, for example, is dark. It doesn't feel at all dark to me. I'm uplifted and danced. Not that classifications are that important. Maybe the issue is that it's fairly underground and maybe that's a good thing.
Electronica is more of a umbrella term to most types of electronic music that's not really geared towards the dancefloor as where ambient is more specific. Ambient music is more focused on atmosphere over song structure and beats/leads and need not be limited to electronica. Ambient Electronica: https://www.youtube.com/watch?v=jgmXnrL19Pw"]https://www.youtube.com/watch?v=jgmXnrL19Pw Non-Ambient Electronica: https://www.youtube.com/watch?v=u_1ZTZCa0o4"]https://www.youtube.com/watch?v=u_1ZTZCa0o4 I think the amount of subgenres and genres of electronic music get a bit out of control at times but I think a lot of djs may try to use it as an identity and when you do hear the stuff spun live in particular, you can really tell apart some of the different subgenres of music sometimes. As TM said classifications are not necessarily that important but it can help you find music sometimes and give you idea of what a dj/band sounds like.