For the reaction $PbO_2 \rightarrow PbO$, $\Delta G_{298} < 0$, and for the reaction $SnO_2 \rightarrow SnO$, $\Delta G_{298} > 0$. The most probable oxidation states of Pb and Sn will be respectively:

The given $\Delta G$ values indicate the spontaneity of the decomposition reactions.

1. Lead (Pb): The reaction $PbO_2 (+4) \rightarrow PbO (+2)$ has $\Delta G < 0$, meaning it is spontaneous. This indicates that the +2 oxidation state is thermodynamically more stable than the +4 state for Lead. This is due to the inert pair effect, where the $6s^2$ electrons are reluctant to participate in bonding.
2. Tin (Sn): The reaction $SnO_2 (+4) \rightarrow SnO (+2)$ has $\Delta G > 0$, meaning it is non-spontaneous. This indicates that the +4 oxidation state is more stable than the +2 state for Tin.

Thus, the most characteristic states are Pb(+2) and Sn(+4).