Attend an international conference during PhD? How to know I'm ready (or not) to attend/answer a call for paper?
From my experience, it's much more useful and rewarding (even for people following your talk) to present a non-finished work than a completed one. As you said, people may come with an interesting opinion or fact you didn't think about and that may improve your study. Moreover, I found much easy and stimulating to talk with someone asking for suggestions rather than presenting a finished work. In this case, they're probably not interested in my opinion anyway.
I attended couple of big international conference and the talk I remember the most was from a guy who didn't even went to the field site to collect samples yet :)
That said, if you think some people may be interested in copying your work and publish it before you, that's a big no-no.