Superstripes are still pretty popular. They don't seem to last when I see their ads posted. Unfortunately sparks and specters can be tricky to identify, so I wouldn't recommend them for a starting breeder unless you've seen quite a few specters/YBs in person and feel confident you could distinguish them from normals. Or any other specter/YB combos for that matter.
I'm personally not a fan of Pumas so I haven't really been following the market for them. Most of my interest has been on highways/freeways than any other YB complex. If I were to add a snake to my collection, it would have YB and banana, maybe a pos het clown or pied. Then in a few years when she's on her way to reaching breeding weight, I'd "invest" in a gravel male, or freeway/highway, or a super gravel. Since I can't afford any of those at the moment, I'm going to stick with what I've got.