But some of these "S" Arms have their "Birth" only from Design reasons.
Or marketing reasons. For the last 20 years, a new arm wouldn't be taken seriously unless it has a straight shaft and integrated headshell. But back in the '60s and '70s when high end turntables descended from professional radio gear, it wasn't considered a serious tonearm (and therefore wouldn't find a market) unless it had a detachable universal headshell. And on a 9" arm, that meant the wand had to curve.
One could say that--*all things being equal*--a straight arm with integrated shell has an advantage. But "all things" are seldom equal. The Rega RB300 is a highly regarded tonearm, especially for the money. Its strongest point is probably its straight, tapered tonearm shaft with integrated headshell. But it has other vulnerabilities such as unadjustable VTA, a VTF spring that's prone to resonate according to some users, and iffy azimuth.
Compare it to an old-school S-shaped tonearm such as a Technics EPA-100, and the Technics has advantages in lower bearing friction, a double gimbal design that maintains azimuth alignment better, a titanium wand that cheats conventional rigidity-to-weight expectations, and perhaps most wonderful of all, dial-in damping to accommodate a wider range of effective mass/compliance ratios.
Economy of scale comes into play, too. That's one reason an RB300 can be considered so good at $400. But if a company found the market potential to scale up to make 3 times as many per year, they could afford to make a better tonearm from better materials, closer tolerances, and more features at the same price.
Is the RB300 a better arm *simply* because it has a straight arm and integrated shell? In this case, probably no. Would an EPA-100 be better with a straight wand with integrated shell? Probably. Enough to tell the difference? Who knows?
Then there's the issue that "different" isn't always "better." At a given price point, a straight arm might have better imaging and leading edge transients; another design might have deeper bass or richer timbres. If you're only listening for imaging and treble, you'd conclude that the straight arm is "better." But someone else listening for the body of the tone might prefer a different tonearm for sounding more timbrally accurate.
