Does Kal-L retain his PC Superman strength as a Black Lantern? I don't see why not. On paper I think we gotta give this one to Kal-L. I mean he is currently taking on Kal-El and Kon-El pretty well so far...
Much as I agree with Atphantom about GL: Rebirth, the big difference here is that Johns has a hard on for Hal Jordan and little respect for Kyle, thus sweeping Kyle under the rug. Wally, on the other hand, is one of Johns' very favorite characters and he wrote about the guy for five years. I think he's too attached to Wally to undermine him so.
Until I see evidence to the contrary, I'm gonna assume Wally is faster.
They will never run in competition, it isn't convenient for none of them.
"We'll probably never find out. Before Rebirth, Wally was much faster than Barry. Now Johns has updated him to a similar speed level to compensate for the 20 years difference. Now he'll probably keep them in the same relation as Hal and Kyle. For ten years there was talk about Kyle surpassing Hal and being a better lantern, and after Rebirth that was shoved under the carpet, and they have been at the same rank since. "
Good points, thanks. Yeah, now is different. Barry is probably, again... the man fastest alive.