Question, is it better to baton pass speed or an attack stat? I was thinking that you pass speed to get priority but I am not sure.
There are two main reasons to boost.
1) to become so powerful you crush through walls
2) to become so fast and powerful that you can outspeed offensive pokemon and 1 shot them (this is known as sweeping)
the second one is a lot harder, and wins games rather than just breaks down defensive cores. See if you get +4 attack you'll 1 shot anything, but chances are the enemy has a check that's faster and has a type advantage and can KO without taking any damage. With speed however, you can clean up sufficiently weakened teams, even if they have 4 or 5 mons left. So why use so many turns just to pass attack when you're really only going to KO one Pokemon. It's much better to just have use the boosting move yourself if you want to break down walls, plenty of viable Swords Dance / Nasty Plot sets exist.
Passing speed is a bit awkward though because then you'd need a speed boosting move, and baton pass, and the only point of have a speed boosting move in a set is to sweep the opponent which you can't really do with just two attacks. Which is why you'll pretty much never see a set like that, whereas passing boosted offensive stats makes a bit more sense, as you threaten to wallbreak with just two moves, then baton pass to another mon that can act as a wallbreaker. There's also the fact that passing attack to a priority user basically doubles as sweeper + wallbreaker.
I'm kind of rambling now, but I think what you should keep in mind is that they don't do the same things, passing speed pressures offensive teams and can sweep lategame, but doesn't really do anything against a bunch of walls, while passing offensive stats is much more threatening to walls, and works very well in tandem with priority users. Really the only viable speed pass is probably Scolipede, and passing offensive stats can be effective, but it's definitely a more advanced tactic because it's not worth the turns without careful planning.