Would there be a reason to cast a higher level version of a spell if there is no difference between it and it’s lower level version?
For instance:
Speak With Animals II seems to be the same as Speak With Animals I. There are other examples with other spells, but is there a reason to cast the different versions? Cost seems the same, effect seems the same…
Both directions work since the mechanics of Counterspell function based on the spell slot used to cast. Same or better spell slot autocounters; everything else is a spell attack roll against 10 + the spell slot of the the cast spell.
Edit: I probably shouldn’t have use spell attack to describe it but it’s basically the same minus the equipment and ability bonuses that apply to attack rolls specifically.