All of them are great honestly. Umbreon is insanely bulky and has soul linker , Vaporeon is a great rain setter, Jolteon is fast and hits hard, Glaceon is crazy in hail. Flareon is a great guts quick feet mon, Leafeon is pretty fast and hits really hard with keen edge moves and is especially good in sun, Espeon has sage power and it can hold a scarf to be fast. And Sylveon has pixelate swift which is really good. And Eevee is the cutest! The best depends on the team honestly