Who is better, umbrion or porygon?

for pokemon heart gold, i am in the game corner in celadon, and i was wondering if i should get eevee or porygon (which would take place of togetic). My eevee would most likely evolve into umbrion, and im not sure what i want my porygon to evolve into. Also, how does togetic evolve? i gave him the shiny stone and leveled him up twice (he is currently 40) what did i do wrong?