Ultimately, the format doesn't matter so long as the product is viable and entertaining.
But I voted for streaming show for a couple reasons.
First, Clark and his setting benefits from long-form story telling that can delve into his psychology and philosophy. Movies, especially action films, move too fast for most film makers and actors to accurately dig into the true nuance and depth of the Super cast.
A show also has the potential to remain a major talking point longer. A movie will dominate a discussion for a few months, but a high quality and popular show? That will dominate a conversation for years. Just look at how long people talked about shows like Game of Thrones or Lost. It would do Superman a lot of good to have that kind of sustained, positive attention on him and a movie just won't provide that.
And finally, a show's smaller budget means it has to rely on something other than big action set pieces to be successful, and when they do show up those big action pieces seem more impressive. A show would force creators away from the gratuitous displays of power and force them to find new avenues to showcase Superman's capability, while making his feats seem "bigger" because they happen less frequently.
Ideally, for me, I'd like to see a Golden Age adaptation. It solves a lot of problems with the character while providing a chance to re-focus. It'd allow the show to deal with some topical issues via the lens of a period piece, which gives it more wiggle room with audiences; allegory avoids a lot of argument that the actual topic would create. I'd love to see a show that borrows from the original comics, the Fleschier cartoons, and more modern updates to the OG like Smashes the Klan and Morrison's opening Action arc. Such a show could easily give us 3-6 high quality seasons of content without running out of road, explore topics people wouldn't necessarily want a modern day, contemporary Superman to tackle, and the Golden Age power levels are far easier to pull off on tv while also providing a sense of physicality and presence that the higher level powers like flight don't convey in as primal and powerful a way.