What is the best gauge of electric guitar strings for a Beginner?

For beginners we usually recommend:

9s (9 gauge) for playing rhythm and lead guitar - e.g. Ernie Ball Super Slinky or Rotosound Roto Pink

10s (10 gauge) for playing mostly rhythm guitar - e.g. Ernie Ball Regular Slinky or Rotosound Roto Yellow

Ernie Ball 2221 Nickel Regular Slinky Electric Guitar Strings 6 Pack

D'Addario EXL110 Nickel Regular Light Electric Guitar Strings 3-Pack