Although these coins were heavily used in the early days of the Pokmon TCG, todays players generally prefer to use dice as their randomizer tools because of their accessibility, so coins have fallen out of competitive popularity
For example, there can be cards that appear in one type of booster but not the other
Then the player can draw 2 water energies
Please, as always, remember that EDHREC is useful but its not perfect
(2021-09-24) If Borrowed Time leaves the battlefield before its enters-the-battlefield ability resolves, the target permanent won't be exiled
Alphabetically, here are all the cards that either are myr or make myr tokens: It's interesting to note that Coretapper is the only Myr that doesn't have the word Myr in its title