Jayne: I agree that curved sopranos can be heard better by the player, especially in a loud ensemble. And, they carry more easily on airplanes. But other than that, I find absolutely NO differences. To me they weigh the same (having the same length of tube and the same keywork (assuming a horn keyed to hi-F and above). Oh, there IS the bell brace - so add less than an ounce.
Tonally? You'd be hard-pressed to identify my curved soprano on a recording - of course a guess could be right 50% of the time.
I've had curved sopranos with terrible intonation (Chinese and Taiwanese, mostly, although a vintage Conn was poor, too). But I've also had straight sopranos with poor intonation . . . the major-brand instruments of today (straight or curved) should play well. I think the Trevor James is Asian-made, and a few years ago there were some favorable postings about it. Before you buy, have a trusted friend try it or at least have a player at the the store show you it has a good scale from top to bottom. Yes, a good player can blow past those issues but at some point you gotta rely on someone other than yourself if you don't play. DAVE