I've used splitcam for over a year, and it definitely lags. OBS has more options, and you get way fancier and more creative with it. Splitcam is pretty simple, for the beginner, but lags hard for streaming. I would love if they didn't because they have some awesome, less work-intensive/learn-intensive features. So think simplicity splitcam, but ultimately better outcome w OBS.
Due to the lag OBS is definitely more worth the time, as far as quality output and placement on these sites go.
However, Splitcam has some real awesomeness, and potential to it.
(For reference I hardwire in to fiber optic internet, and I have a low to mid-end gaming PC).
All of the above was for streaming live.
For clips I like Davinci Resolve and Wondershare Filmora + Wondershare Uniconvert.
Davinci resolve has a bit of a learning curve to it too though, at least it did for me, much like OBS.