This is an ongoing debate. I personally feel that they are simply 2 lines of the same morph.
Both sides agree that both have the same mutated allele as they both are part of the BEL complex (if you breed them together you get a Blue Eyed Lucy) they are both base morphs, so they come from the wild and are not produced by combining morphs.
The other side sees butters and lessees the same way that the Mojave and lesser are, 2 seperate morphs that are similar because they both have a mutation of the same allele (but the mutation is different)