[c-nsp] design ? - two POPs, same AS or different?

[matthew zeier]

This is a design question and I'm not sure the "best" way to solve this - 
looking for suggestions.

I currently have a site in San Jose announcing a /22 out of my larger /20 
behind a particular ASN.  In a couple months I'll be opening a second site 
somewhere in Europe and announcing another /22.

I won't have any physical connection between each site but will need each site 
to talk to each other.

Would I be better off getting a second ASN, putting up GRE tunnels and peering 
or use something like allowas-in?

And to add to the complexity, at some point in the future I'll be anycast'ing 
a portion of that /20 out of each site.

Thanks.

- mz