Snap is a much bigger question mark. So far their plan looks to be "Do what Facebook did, only for AR/VR". Except Facebook and Snap will be splitting the market; where Facebook had no competition and absolute dominance before they IPOed. Facebook is obviously playing to win on Snap's home turf. Even if Snap is successful, Facebook will make it very expensive for them.
I'd argue Snapchat delivered one of the first mainstream AR 'hits' - many of my friends can't get enough of their AR photo filters. To be fair, many of them are extremely impressive tech demos, fluidly augmenting the user's face in real time video. Whether that's a meaningful strategic advantage is another question!
Facebook is already a top aggregator -- and already has a lot of preference data from billions of users. Those are enormous network effects, and even if Snap is hugely innovative, Facebook will always be able to replicate Snap's products much faster and better than Snap will be able to replicate Facebook's network effects.