Top prof will prefer research exposure. If you are applying to top institutes then it is likely that your competitors will have good amount of research exposure.
@sudarshan (last post) - prof have already too much work to attend along with their personal stuff. They can still agree to work with other guys if those guys have done something substantial to attract prof's attention. I think you should try some research area in which you can start alone. Once you fix and start working on a particular problem, try discussing it with the authors of papers which address that problem. Personally I think that it would be gr8 if one of the author is a grad student. Then once you do all hard work say 4-8 months, either you will be having some results or almost towards it. If nothing happens, then write a survey paper and if relevant then your ideas which failed, e.g. This problem does not have a greedy solution or the problem is at least in EXP. At the end of all this, you have research exposure. Upload your survey paper at arxiv and link it in your cv/resume.