Yes, it matters.
Slims have
PVR-802W, also listed as HS-430. Fits all slims cept the 9000X.
9000X is TDP-182W, only fits the 9000X model.
Fat ps2 use.
KHS-400B
KHS-400C
KHS-400R
HD7.
400C and B are interchangble. B won't physically fit in anything above a V4 though.
KHS-400R and HD7 are interchangable.
PS2 knows what it is suppose to have, so swapping a 400C for example into a unit with 400R won't work.
There is homebrew to change the entry on the ps2 eeprom for laser type, so you can stick a 400C in an R unit or R into a 400C, but I can't say anything more than that because of the terrible rules here.