Bad or good idea to change jobs before applying?

Hello Greekmythology,
In my opinion, changing jobs won't do a lot to help you from an admissions standpoint for Round 1 since you would just be starting the job around the time that you will be applying for b-school. However, as you mentioned, if you believe that the new job will really help you gain more analytical skills to help position yourself better for finance jobs after b-school then it might make sense. I would warn you, though, to think about how this change could affect your recommenders since you want to be on very good terms with the people writing your letter of recs. How will your current managers respond to the news that you're leaving? Since you would just be starting a new job (if you take the mortgage company job) then your new manager likely will not have a lot of time to observe your work and likely won't be the best person to write your letters of rec. However if you apply for Round 2 then you would have about 6 months of experience in the new job which will give your manager more time to get to know you and be able to complete an insightful letter of rec.
Before you make your decision, think about the pros and cons of your choices and how they will impact your b-school application. Are you set on applying in fall 2015 or would you consider working another year if you take on a new job? An extra year would give you more experience in a quantitative role as well as you would have more time to make an impact in the new organization that you would be joining. Hope this helps with your decision-making process.
Good luck!
Dina