Is it better to have a single-author paper or a joint-authored paper? I am a new graduate student and I am about to start writing my first paper. Some of my adviser's other students have been working on similar topic to what I have been working on and he has been pushing us to combine our results into one paper. However, I feel my results could be a paper on their own. I want to start beefing up my CV so that I can get extra funding and, hopefully down the road, a research position but I am afraid that if I am only a coauthor on a paper it won't look as good as if I am the sole author (especially since I worked completely on my own for my section).

So my question is: would it be better to try and publish a paper in which I am the sole author or would it be better to try and publish a slightly better paper in which I have 2 or 3 additional coauthors? Do funding selection committees and the like give precedence to people with papers that they are sole authors over ones who have coauthors?

Edit: My field is math, in case this matters.
You should really listen to what your advisor says. "...he has been pushing us to combine our results into one paper." That about says it. Your advisor knows what works and what doesn't work as a paper in your field. He also knows (presumably) about the scope of your work and how it fits into what you and the other students have been doing. 

There is little downside to this. The importance of the paper to your career has far more to do with how well received the paper is than with how many authors there are. Having more authors means the paper is stronger, means you have a network of people to help rewrite and deal with any negative reviews you may get, and (as suggested in Peter's answers) it shows you can collaborate with others. 

It would not hurt to bring this up with your advisor, make your point (ask your question), and see how the advisor reacts.