Key difference between scarcity of $DCR and $BTC is #Bitcoin immaculate conception, time alive (network effect) and block reward distribution.
21Million, predefined schedule and S2F path are equal.
If #Decred does NOT conform to this S2F model, perhaps $DCR is not developing a valid monetary premium and may be discounted against $BTC.
However, if $DCR DOES perform, especially relative to $BTC in the early days (apples to apples), this becomes a convincing argument.