I'm not sure what you mean by having a diploma and not a degree, typically those are equivalent.

If you have enough credits to get the diploma but have not satisfied the degree requirements, then that is a tougher decision. And it will depend on how much value you perceive in meeting the additional requirements, but as PG writes running up the stairs (take the harder path) usually has a bigger advantage.

That does not mean you can not work full time. Lots of distance education courses available. Check with your school and find out the rules/regulations in this area.

Also you can network while in school, possibly this can lead to a company/start up that will let you start work while you finish your schooling.