Will I see any marked improvement in call quality if I replace my 10 year old PAP2T with an Obi device?
They both use the same basic VoIP standards and technology. If the PAP2T is still delivering the same call quality as when it was new, then you will find no, or no significant, improvement in call quality by switching to an OBi200.
Do VoIP codec standards define precisely how a dropped packet should be handled? It's been quite a while, but I remember thinking shortly after I converted from a PAP2T to an OBi20X that the OBi's voice quality when dealing with a stream of dropped packets seemed smoother than the 2T's.