Advanced Moves; Requires vs. Replaces

Sorry if this has been asked before in a previous thread. If so, people can just point me in the right direction rather than repeat it all again here.

I've been making my own Dungeon World Playbooks for the classes in the Beta rules (Japan uses A4 paper, not letter) and saw something interesting in the Advanced Moves. Some moves note that they require the player to have chosen a certain move before they can be taken, while other moves say that they replace certain moves. I'm wondering what the difference is, and if it's even necessary.

"Requires" is fairly easy to understand. You can only take the better version of the Move (usually in the level 6-10 Advances list) if you've already taken the lesser version of the Move (usually found in the 2-5 Advances list). The Requires Move usually adds an additional effect to the "base" Move, allows you to choose a second option, or somehow builds on the "base" Move.

"Replaces" is a bit more confusing though. Does "replace" mean that the player crosses the "replaced" move off their sheet only if they've taken it as a previous advance? Or does it mean they cross the "replaced" move off of the list of advances even if they haven't taken it as a previous advance? I know the result is the same; a better version of a previous move, but I'm anal retentive and like to know exactly how things work.

We play that replaces does exactly that, wipes the old move and replaces it with the new one, thus preventing exponential mechanical advantage. Whereas requires allows you to have both moves and thus both fictional  / mechanical benefits. Make sense?

@ HyveMynd: That's a great question!  Some of my players have also asked if "Replaces" means that they must have previously taken the replaced move or if they can take the more advanced move without ever having taken the replaced move.

I lean towards must have previously taken myself (so that becomes "Requires + Replaces"), but it would be good to have that clarified.

That's what I get from reading the book. I think it's even directly stated but I can't recall where.

I tried rewriting some of the Replaces advances as Requires (with clarification in the text) for my homemade Class books last night. It sounded clunky. For example, the Fighter's Bloodthirsty Level 6-10 Advance became:

Bloodthirsty
Requires: Merciless
When you deal damage, deal +1d8 damage instead.

Basically, all the changed moves would need to have "instead" in there somewhere. Otherwise it could sound like the two advances stack with one another. "Whoa! +1d4 and +1d8 when I deal damage if I take Merciless and Bloodthirsty? Yes, please!" So after doing that, I realized that just tagging the Advances with Replaces: X is probably the easiest solution. Obviously there's a reason Sage and Adam are successful game designers and I'm not. LOL.

Still, just because I'm anal retentive crunch monkey who likes to know exactly what's happening with my mechanics, I'd like that clarification. Does the player have to take the Advance that the better Advance replaces (like Admutt's "requires + Replaces" suggestion), or does "Replaces" simply indicate that the "lower" Advance is no longer available to the player?

It's a tiered requirement.  Requires means "You need to have this move to take this other move, and you keep both" where as "replaces" means "upgrades the existing move, which you have to have first."

Stupidly-unclear in the book.  I filed a "bug" for this today!