Lazs mate, you don't know enough about this stuff.
My GSX-R600 will do around 160mph. Not 190mph. That's Honda Blackbird / Suzuki Hayabusa territory and those aren't sportsbikes, those are sports-tourers (marketing men wouldn't agree, they call em hypersportsbikes) that go very fast in a straight line and get all squirly at the sight of a corner.
My bike goes round corners like it's on rails cos it's lighter, only a 600cc machine, 350lbs without me on it. You'll find the smaller and lighter the bike the better it'll corner, Aprillia RS125s are probably the fastest cornering bikes on the planet but they wont go much over a ton in a straight line, downhill with a tailwind.
Now think about this some more mate. If the air resistance of an unfaired bike will slow it's top speed then it'll also slow it's acceleration as well. Right? No traffic law in this country mentions acceleration. The speed limit might be 60mph (for example) but I get there from a standing start in under 3 seconds and Mr Plod can't do anything about it.
I
also much prefer the protection from wind you get on a faired bike over an unfaired. Mate of mine once rode an unfaired Suzuki bandit over to Holland for a visit and we both rode back to Blighty.......ok, he's a big lad (6'4", 280lbs) but damn......the weather wasnt great and he was acting like a sail with no fairing to deflect the wind away. This is at motorway cruising speeds (100mph ish - attitude to speed isn't quite the same in Britain as it is in Europe or the US. At 100mph you'll still have people overtaking you).
No so, it's not just about top end speed however, to quote you once more "you really do need that extra last little bit". Nope, I don't
need it. I
want it.