I personally prefer to have steady, stable employment over seasonal work. Keeps me busy, out of trouble, and give me a steady stream of income to allow me to continuously fix things on my YJ as they break
Also, working a more stable job looks better on your work history, as it leaves fewer gaps. I would venture to guess that employers, in general, want to hire people who stick with their employer for longer periods. Most don't want to invest any time in people who appear to job hop or otherwise don't hold steady jobs. A history of seasonal positions might be an exception, provided that the seasonal work is related.
That $1/hr for the summer seasonal position might not make that much of a difference once the tax man gets ahold your your paycheck.