I would invest in Snapchat at any valuation that is below Facebook's. Sounds crazy but the first time I opened the app (on a friend's phone) and it landed me on a camera screen (almost forcing to contribute content to use the product) I felt like the guys were going to win whatever space they were in.
My understanding is that Snapchat is cool among teenagers and tweens, whereas Facebook is old news. I've watched people "use" Facebook and it seems to provide negative value. If you are interested in diverse things your feed will be a total freak show, images of deformed penises (Medizine groups have those) mixed with 5 step cooking gifs. Snapchat seems to have a much better focus on stuff people actual want to do, whereas the core Facebook experience seems to be just aweful and outdated.
