Well, I think you are more likely to find a better job offer having done a residency. That was definitely the case with me. But that isn't to say you won't find an as good or better job without one. I feel like it puts the odds more in your favor.
The job I was looking for in particular was in an optometry/ophthalmologhy group practice. The residency I chose works particularly close with the ophthalmology residents. I attend all the morning lectures with them, work the same clinics as them and speak at the same confrences as them. Besides the surgical training, I am getting very close to the same residency training as them - for the year I'll be here. That was particularly interesting to the group that hired me.
As far as specialization, I think that you will become much more comfortable with things you may have only spoken of in school, and only did a couple of times at best. In my own case that was true. Two to three day a week I work in a specialty contact lens clinic. It isn't uncommon for us to fit four to five cone patients in a day, actually it's almost always the case. We routinely fit two month old infants with lenses, post-graft patients, Salzman's patients, etc. These are all things that after having spent a year here, I feel very comfortable with. I don't believe that would be the case not having done the residency. I feel like doing a residency was one of the best decisions I have made.