I am looking into beginning hawza studies next year in either Najaf or Qom but I am not sure which city I should go to, both are great so it makes the choice hard.

In your opinion which city would be best and why?

If you could also list pros and cons of both that would be much appreciated.

Each has pros and cons.
In Najaf you need to know Arabic.
In Qum you will spend some time learning farsi.
In Najaf you will be next to shrine of Imam Ali (a).
In Qum you can study more subjects as the hawza has not gone through too much difficulty over the years like Najaf.