Probably Electric for me. Don't really have a proper reason, I just generally loved Electric Pokemon more than most other types. And Jolteon exists, which is one of my favourite Pokemon and is also Electric Pretty fun to have super fast speed and have Thunder just troll everyone lol.
Slyveon is better
I like Flying, Water and Fairy type the most personally.
Flying because I love birds, and most flying types are based on birds.
Water because there's just so many Pokemon that are water type, it's hard not to like a lot of them. They're also generally the most balanced seeming type in terms of stats to me.
Fairy because cute (for the most part)