As you mention, the 202 provides a second phone port, so it will support two phones simultaneously. It also has some additional router features which would probably only be of value if you plan to only do VoIP over your Internet connection. Even if you won't make much use of the second phone port, I've found it useful for testing changes made to the alternate phone port or VoIP service.
If you are planning to buy a box soon, be aware that last Saturday, Obihai sent out an email to the effect that the OBi200 will be on sale briefly for $29.95 from Amazon. From that email:
( http://www.amazon.com/gp/goldbox/ )November 30th ONLY at 6:30AM to 10:30AM PST
Save on the OBi200 - $29.95 from Amazon – Save Over $60 Off List Price!
On 11/30, Amazon.com will feature the OBi200 on sale at $29.95 with free
shipping, as a Lightning Deal. Look for it in the 'Today's Deals'
area of the Amazon web site. Click HERE ( http://www.amazon.com/gp/goldbox/ )
to see Amazon.com's 'Today's Deals' and be sure to come back to this link on
November 30th, to get the deal. And remember, a Lightning Deal only lasts a few
hours and could sell out very quickly. Keep your eye on the Amazon.com Today's
Deals page so you don't miss out!