I'm not sure which one to choose so it all comes down to job prospects and pay. In the future, which is more likely to have better job prospects and a higher pay?
In the US, the Bureau of Labor Statistics, an office inside the federal Department of Labor, publishes an Occupational Outlook Handbook for various technical and non-technical occupations:
Geologists (or to use the term 'geophysicist' from the handbook), tend to make a lower salary than petroleum engineers. Both occupations are in some demand because of an uptick in exploring new sources of petroleum in the continental US. However, employment in the energy sector has for a number of years experienced periods of boom and bust as the price of oil soars or drops. You may find yourself competing for a job as a geologist or petroleum engineer against people who were laid off after the last crash who have a wealth of previous experience to bring to a job.