I've never had the Fallkniven, but I've had both of the BM 211's (D2 & S30V) & I've had other FBs at the Fallkniven's size (Just under 7" OAL). The BM works surprisingly well & easily concealable.
Aside from the size, the WM1 has quite a bit more blade than the 211 (I believe close to 3/4" more). However, I think small size for neck & even horizontal carry is more important than blade length, but it also depends on your priorities.
Personally, for a neck knife, my 3 favorites are:
HAK (HideAwayKnife)
Spyderco Swick or the SPOT
Emerson La Griffe
The finger hole is a big help on a small knife, both for retention & indexing for neck carry.