Most of my loadout uses dark colours, but my MP9 still looks like an unrelated purchase from a different collection. I want something with a clear visual feature without covering the entire weapon in bright paint. Rose Iron caught my attention, although Hydra and Deadly Poison also look interesting in screenshots. How would you narrow those options without simply choosing the most expensive one? I am willing to spend a little more for a design I enjoy, but matching the rest of my equipment matters more than owning the version that attracts the most attention in a trading discussion
I would decide how much contrast you want before comparing prices. A dark loadout can work with a small coloured detail or with one bright weapon, but those are different choices. Put screenshots of your current equipment beside the candidates and see which one looks intentional. You could also hide the prices during that first comparison so they do not influence your taste. Once you have two favourites, inspect the actual items being sold. My preference would be to buy the one whose main design remains clear at normal playing distance, rather than paying extra for details I only notice in a close image.
Rose Iron seems worth keeping on your shortlist because the article describes a rose and thorn design against a matte black background. Its other examples include Hydra, Goo, Bioleak, and Deadly Poison. That gives you several ways to compare colour and decoration on the same weapon. The article at https://ventsmagazine.com/2021/11/02/top-5-best-mp9-skins/ contains plenty of useful information and links to DMarket, a marketplace for buying skins. The prices in the piece date from 2021, so use current listings for your budget. Compare the specific item images before choosing. You can then explain your decision through the design you prefer, rather than the position it holds in somebody else's ranking.