It's a matter of degree.  Also, orthognathic surgery, while it can
address the gummy smile, has the ability to more drastically change the
configuration of your face.  If your upper jaw is too long, crown
lengthening won't do anything to address that.  Obviously you're limited
in how much gum tissue and bone can be removed in a crown lengthening
procedure.
    In short, you should be very informed about exactly why orthognathic
surgery is being done.

Steve

Hello

Orthognathic surgery is the onlyway to eleminate and to reach over the
time a stabe result. Normally in cases like you a vertical excess of
the upper jaw can be observed; that means it is problem of bone-growth.
I never consider crown-lengthening; only in patients with short teeth
gingivectomy can be considered. Bone remove in the frontel upper zone
can result in an open bite, that means that by intruding your frontal
teeth, frontal occlusion can be lost.
As your problem is an esthetic one, I suggest you to search an
orthodontist which is specialized in presurgical orthodontics (in
totally 1/2 year of orthodontics), and a maxillofacial surgeon (with a
lot of experience in esthetic orthognatic surgery). You have to speak
with orthodontists AND maxillofacial surgeon  - everyone is specialized
and can tell you exactly in which treatment consist. Do not beleave
only in less-experienced general dentist.
if you would like more information send me an email!