If you were to pick option 1, can the courses you take be transfered towards your master degree (assuming you would enroll at same university)? Getting course requirements out of the way during a working year would leave you just the research component to finish after. Plus, can this research help you with your research of interest for the degree (fullfill publication requirement? allow you to learn more about the subject?)?
As easy as it is to just jump to option 2 and "get that degree".. I wouldn't rule out 1 without doing some further research into what you can really gain from it other than more money and better benefits.