Well the obvious answer is that I want the effects of Melanotan 1 and not 2
But as far as the tanning specifically, I'm not blinding white so slower and more minor tanning is preferable, and I'm worried about the increased likelihood of my freckles/dark spots darkening too much with 2. This could happen with 1, but 1 seems to be better for sunburn and damage protection. 1 is theorized to reverse heart damage and decrease amyloid beta plaques. Lowers blood pressure and neuroinflammation. It works on pancreatic receptors and increases metabolism through that route.
2 seems more ideal for those looking to get super dark + erections + stronger appetite and food addiction suppression as their priority. It can raise blood pressure. It could be a good choice for autistic people who want to be more social and relaxed in public as it works with a different receptor associated with that.
There is some overlap of effects between them and it comes down to what you're most interested in taking it for, but I personally think 1 is underrated and that some people just jump on 2 because they're too impatient to tan more slowly, lack awareness of 1, or are just mostly about the erections/libido boost (which is fine but not a top interest for me). Both of them could probably use deeper research studies on humans rather than rat studies.