Both of them do a good job of showing up the expansions new mechanics and key features, and after playing them I dont think a third one would have been necessary, especially because it would have just been another Ruby/Emerald like last time
I have pustules of the great Ratadrabik, very cheap
Black is stacked with great two mana removal options and so there is little need for the lesser ones despite those being objectively better than many of the frequently played alternatives in other colours
Things like Yorion, Sky Nomad and Airbender Ascension make for some cool interactions
The Etalis Ive found that Etali, Primal Conqueror is the better version of Etali due to its immediate impact on the board and the potential game ending threat it poses once it's flipped
Please note, though, that the Legendary Rare Backgrounds are not in this list