As Ken so rightly said, it's about what you want from a bike.
It is also, a bit, dependent on you.
You'll need to find a Triumph dealer, and sit on, and test ride both the Speed and Street Triples.
ditto for the Buell and Kwaka.
I tried the Speed triple, and, had I been 3" taller, and twenty five years younger, fitter (and sillier?) I'd have bought it, but, as I am, I am happy with it's little brother the Street Triple.
Actually, that's not really true....25 years ago, I went out and bought a Kwaka 750 Turbo!
I don't know what you ride at the moment, but, from your comments about insurance costs and fuel economy, I think you might like to investigate the cost of tyres for all the bikes that you have mentioned.
Any of them will eat tyres with gay abandon if you are remotely enjoying yourself and will cost quite a bit to keep properly shod.