there are lots here with more detailed info than me, but Conti tubulars have butyl inner tubes, which is not ideal for lowest RR. Tom A has lots of good things to say about the new Zipp tubular (developed in conjunction with Cont, I think...) which have latex inner tubes.

If the Schwalbe Ironman has a latex tube that would be good. Or Zipp. The Conti tubulars have butyl tubes and also have lower tpi casings than the clinchers.

Don't go too fat if speed is your priority. Not so important on the rear, but very important on the front.

unfortunately they are not equal. their tubular are not quite on par. not sure why they don't have latex tubes with the prices they charge.

of those choices I would go with the Zipp Tangente. IIRC there was a thread on here not too long ago about the Schwalbe claiming to have latex tubes, but when one was holding air a real long time the owner cut it open and found a butyl tube. I don't recall how that turned out.

Or you could also go with Vittoria corsa evo tubulars. they are pretty fast and proven to hold up fairly well.

I ended up ordering the zipp tangent sl speed 700x24 tubular for installation when LBS receives it. Looking forward to using the disc.