If you plan to keep your land line (I assume that land line is PSTN, and not VoIP) - then I would recommend OBi110. Obviously, if your PSTN provider doesn't supply Caller ID, OBi won't be able to "invent" it, but it is convenient to have one phone for both PSTN and VoIP calls.
On the other hand, if you plan to have more 3 or 4 accounts (GV or SIP) - then you need OBi202, since OBi1x0 only allow you to register with 2 providers.
And if you want both (single phone for PSTN and VoIP calls; AND more than 2 providers) - you need 2 devices