As others have mentioned, once water can penetrate the vinyl thru a crack it's at risk for rust.
If you were to spray the whole top, you'd need a plan for spraying at/near the stainless trim at the windows and gutter/driprail. IMO, that juncture would look like crap unless you masked very the stuff filled the gap nicely.
My white avatar Fury kept its vinyl top until the early 2000s before it started to split.
I stripped it all off, did some cleanup of some extremely mild rust, and primed/painted with Rustoluem. Used a narrow quality brush for the edges, then did the rest with foam rollers, both 9" and a narrower one to go around the back window. From a distance it looks quite presentable, and most folks outside the classic car arena don't know the difference. I have far to many projects to afford to do everything 'by the book' correct.
That paintjob didn't last forever, though. It faded a bit by the time this pic was taken, so I re-did it last summer. Took probably 3 hours start/finish and I'm good for another 10+ years.