I'm not a lion guy myself, but I like the design of Solgaleo's mane. It's not covered in gaudy doo-dads, either, which is great. Lunala is probably the better one, though. Can't go wrong with a spooky moon bat.
As for the Necrozma forms, I gotta say, giant black prism arms are something I never knew I wanted from Lunala. The back of Dawn Wings looks weird, though; what used to be Necrozma's big head is just sticking out of Lunala's back, and that just looks weird. As for Dusk Mane, I like his "antennae" and how what was once Necrozma's arms are now Solgaleo's "wings". That's fun. Also, do the little prism bits on the tail of Dusk Mane kinda make the whole thing look like a manticore? Cause it looks like a manticore to me, even if it's not really a scorpion tail.
Where's our manticore Pokemon, GF?