Oceanside isn’t generally considered a good area of San Diego to buy in – yes, it’s on the coast, but it’s demographics are pretty low end, it’s a long commute to most of the good job centers and attractions in San Diego (with the exception of the Carlsbad area jobs/attractions), it has significant gang issues in areas, an overall poor school district, and is generally considered a lower middle-class area to live in.
Scripps Ranch is considered a well-to-do upper middle-class area, some of the best schools in San Diego (Poway Unified School District, one of the two best in SD), and while definitely a suburban area, isn’t too far out from the main job centers and attractions in San Diego. Drawback is that the particular developments you are looking at are at the edges of Scripps Ranch, which is considered to be a very severe wildfire hazard area.
Between the two, I’d take Scripps Ranch in a heartbeat (and have – lived in San Diego all my life, I’ve lived in Scripps twice. I wouldn’t live in Oceanside unless I was paid to). Just keep your fire insurance up to date in Scripps, and make sure your builder is creating a very good perimeter (and that you maintain that perimeter once bought).
You might also try looking in the Carmel Valley and 4S Ranch areas – both are also high end areas with excellent schools with ample choices in the million $$$ range.