Both devices (200 and 202) have four independent Service Provider configurations SP1--SP4. You can use each of those four SP's with any combination of Google Voice or SIP ITSP services. So yes, one device can host two different Google Voice numbers. The difference between the two models is that the 202 would allow you to have two separate analog telephone lines connected to the device, whereas the 202 supports only one line.
With regard to Google Voice: it's a service, like Gmail, Calendar, Docs, Contacts, etc. All Google services are assigned to a Google account (Gmail address). One Google account can host one or two inbound Google Voice numbers. When using two numbers, all inbound calls to either number will ring the same destination phone numbers or devices, and hear the same voicemail greetings. Outbound calls will use the caller ID of the number designated as "primary". You can switch primary/secondary roles at any time via the Google Voice settings page. So: the two numbers are not completely separate.
If you want two completely independent Google Voice numbers that route to two separate destinations, then you'll need to set up two separate Google accounts. You'd configure one Google account on each SP, and you would route one SP to one physical phone jack on the back of the OBi, and the other SP to the other jack.
