I think it depends on where you are but chances are wherever you are there are more optometrists than ophthalmologists. I am in a city of about 200,000 for med school and optometrists are everywhere: Wal-Mart, Shopko, Target, about 5 in the mall, D.O.C., Pearle, etc.
I want to go into ophthalmology, but I go to an optometrist for my eye exams and glasses. I have never really considered going to an ophthalmologist for an exam. On that same note I recently started seeing a private optometrist instead of going to Wal-Mart and let me tell you i am never going back to a chain-store doc. I know that they are not all bad but the private guy really took his time, was much nicer, dilated me (never happened at Wal-Mart), and had a MUCH better selection of glasses. It was well worth the extra money. Plus my prescription had 'changed' in a year by quite a bit. I sure do see better with my new glasses leaving me to believe that the Wal-Mart guy screwed up. It even felt different, the private doc was like going to the dentist (professional environment, etc.) while going to Wal-Mart made me feel like I was well...in a Wal-Mart.
As far as competition for patients, yes some ophthalmologists do practice optometry and do many eye exams/glasses/contacts/primary eye care infections and the like so there is some, but the ophthalmologists that I have worked with get their most of their patients from optometrists. The fields can be similar but basically they are a world apart. Ophthalmologists are first and foremost surgeons and Optometrists are primary care providers in my own view.