The reason why most people stick with Melanotan 2 is because on a mg per mg level there is actually more Melanotan 2 peptide chains because it has a smaller amino acid sequence. This means that on a mg per mg basis effectively you require much less in terms of milligram weight of melanotan 2 to achieve similar results compared to melanotan 1.
Another great thing about Melanotan 2 being a smaller peptide is that it is much more effective at passing through the blood-brain barrier, as well as increasing libido. This could perhaps make it seem to be a significantly more effective tanning agent.
I remember reading somewhere that a sponsor mentioned Melanotan 2 was a combination of Melanotan I and PT-141. This is simply not the case. Melanotan 2 is structurally different from both and is not a combination of the two. Melanotan 2 is actually almost identical to PT-141 except for PT-141 has an OH at the N-Terminus rather than an NH2. PT-141 and Melanotan 2 are both cyclic peptides and Melanotan 1 isn't.
Just thought I would throw that out there for you guys! Good luck!