I'm going to guess it's the length of the if statement and/or the searching for /secure/ and /largecrate/ in the containertype. I personally prefer a single if statement to breaking it up into several, but I don't mind changing it.
If it's the search for /secure/ and /largecrate/, I'm not sure what else to do.  I have to tell the difference between crates like:
/obj/structure/closet/crate/hydroponics
/obj/structure/closet/crate/internals
/obj/structure/closet/crate
And crates like
/obj/structure/closet/crate/secure
/obj/structure/closet/crate/secure/hydrosec
/obj/structure/largecrate

There's no separate tree devoted to "normal" crates.