Honestly they're both basically the same and the race will be quite close, but I'm rooting for Casten.
Newman is definitely much more left-wing and progressive than Casten. They are a consistent party-line vote, but to say they are the same isn't really accurate. This isn't an AOC-Cuellar type primary, but Newman and Casten certainly have their differences.
Yeah, I suspected Newman was more progressive while Casten was more mainstream, but it's their votes that really matter. Newman is more liberal than the average Democrat but not liberal enough to act like AOC and the Squad and cast protest votes against what the party wants. I mean, AOC and the Squad all voted against the infrastructure bill because it wasn't progressive enough or whatever, but Newman stayed with the party. So I don't think there's a major difference practically speaking, but I support Casten over Newman, partly because of Newman's progressivism now that I've confirmed it.