[barnstenchfartface]

I think I generally prefer when the Riders start out as established Riders. It can lead to more dynamic first episodes (and first quarters) since it allows the story to skip a bunch of steps and just launch us directly into knowing who the Rider is, what they're fighting for, what to "expect" from the show...at least for me, first episode like Wizard's, W's or even Stronger's left a lot more of an impact than I think the alternative would have (though the latter there goes immediately into his backstory on episode 2, it's still memorable to me as it's pretty much literally the only Showa Rider besides the oddball RX to which that applies)

It's not a guaranteed recipe for success or anything, but I still think it also has some benefits just structurally, especially for modern toy-heavy series. Like for Build, the first couple episodes didn't blow me away, but the fact that Build was already established as a Rider was a massive boon to the story, since we could spend more time focusing on secondary characters like Banjou, and it allowed the episodic story to not have to bother introducing like a dozen toys individually because all of that was squared away pre-show. Guys like W and Wizard are experienced and don't have to fumble their way through new forms or finding new toys every other episode for the plot, they can just pull out what they need when they need...it just gives the story a little more room to breathe, I guess?

It's not like shows in which the Rider has to figure stuff out as they go can't do a good job of it or anything, it's not necessarily a detriment to the story ever really. As has been said, both ways have been done both well and poorly. When it's done right, though, established heroes can be more fun, imo.