If I had to choose between publication and thesis, I think I would go for publication. But... Can't you do both? I will be starting a thesis soon with the explicit, achievable goal of publishing work from the project this year... And I also get it as a course (it is a requirement at my college to take five courses each semester to graduate in four years, so this really helps with me being also able to do research and get involved in clubs). I would guess that you could do the same? Are you applying next cycle? If for this cycle, it would still take a long time for your paper to be peer-reviewed and accepted, and it isn't worth too much on your app if it's not accepted.