They both have very stylized and "good" animation, depending on your outlook.
They both are episodic anime, with a few episodes sprinkled in to advance the main conflict, which has been hard to pin down as to what that is.
Both have their own sort of actions scenes, with LWA's being the magic exhibitions and Pokemon S&M's being the pokemon battles.(Also lol S&M)
They both appeal to children, and as such have characters and references that reflect this target audience.(That won't stop a few older people from enjoying it though)
My final and weakest point is that they are both very much mixed bags as far as criticism goes.(But that goes for pretty much any anime)
While I may not like either, that shouldn't stop you from liking them. Chances are if you enjoyed one, you'll enjoy the other.
Don't worry about the loads of prequel anime before Pokemon Sun & Moon or the games, as they aren't necessary to get a hold on what's happening.
Both are airing now and the episodic format is best experienced a bit at a time.
So if you do consider watching, I'd say do so right away or at least before this season ends.(But if you like to binge like I do, go right ahead)