Its all down to personal taste, I suppose the newer mutations will be more desired by people, such as your Anthracites, Black Face etc, I wouldn't mind a couple of those
Rainbow Budgies are quite difficult to produce as if your starting from scratch they can take a couple of seasons to get, they are a Yellowface or Goldenface Opaline Clearwing Blue Series Budgie. I have some birds that are Greywing instead of Clearwing lol but look equally as stunning.
Some colours will always be less common as they may be hidden in the Genes for a few generations.
However personally for me I LOVE Lacewings, I have found these hard to come by but have finally managed to get a couple again, I also wouldn't mind a Blue Series TCB.