100 or 200 Amp meter head?

I am going to place a new service drop and meter head next to my old one and then the POCO will switch it out. My question is how is a 200 amp meter head different than a 100 amp head? I have an existing 100 amp service and it's fine but in the future someone (maybe me) may want more power.
Can I use a 200 amp meter head to supply the existing 100 amp main panel?
They look the same to me!
Thanks for the advice.