Picked Popplio in US. Haven't started UM yet, but I may just wonder trade whichever starter I pick away and play that way.
Popplio because a) Eryizo said he was the better one to go with and b) I wanted to try being a water type starter.
Litten because I already had Rowlet in Sun and Popplio's design just isn't my thing lol I need to get it an everstone so it can't evolve into Incineroar
I picked litten, but I didn't use him past the first trial. I ended up using chimchar, froakie, and treecko for my starters.
Popplio! It was a life saver when I played Sun and continues to be in US. It's honestly my favorite starter. Named my boy Kringle
i choose the grass type starter in every Pokémon game ( except Pokémon yellow ) so i got rowlet. and i am very glad i did because it is a HUGE help late game. that and i got a shiny for ultra moon. sadly not normal moon
Rowlet! As cute as the other two are, I know I wouldn't be starting a new game over so I stuck with the tradition of picking Grass starters.
I went with Rowlet, since I used a Litten and Popplio on my Sun team. I really enjoyed using Rowlet, and I think Decidueye may be my third fave fully evolved grass starter (Chesnaught is still my fave, and Venusaur is still second best boi. Lol). Battling with it really made me appreciate its design.
I chose Popplio since it was one of the better ones for competitive and its evolutions are of a better design that Litten's line, though I liked Rowlet and its line, I just thought that I could use popplio better in a team.
I chose Popplio because I love Water types (and it’s Fairy type later on was useful). And I liked the design a lot. When I got Ultra Moon though, I chose Rowlet. I liked its evolution’s design too.
In both Ultra Moon and Sun I chose Litten because I love Incineroar mostly because I love dark type Pokémon.