Wow...it seems like you are confused on MANY levels.
First, while riding on flat roads, there will be NO difference from a rotational inertia standpoint, real or perceived, between a 404 clincher or a 404 tubular wheelset...assuming "equivalent" tires (e.g. Vittoria Corsa and Open Corsa), of course.
In fact, if using a quality clincher (i.e. Open Corsa or Michelin Pro2Race) the clincher version will ALWAYS be faster, despite the higher weight. On flat roads, the extra weight is basically inconsequential. Actually, for the case outlined above (clincher vs tubular 404s with "identical" Vittoria tires) the clincher version actually has an advantage due to it's lower rolling resistance up to and including grades of 9%. Only THEN does the lower weight of the tubular version FINALLY draw even from a performance standpoint. In other words..."on paper", the clinchers are faster.
Now...why in the heck would you limit yourself to running tubular-clinchers on the clincher set? I'm assuming you mean the Tufos, right? Well...that's just shooting yourself in the foot. I haven't seen any RR data on those tires yet, but judging from their tubular tire performance, I don't think they'd be "anything to write home about". This is mostly due to the Tufo's "tubeless" construction where a butyl bladder is built into the middle of the tire. Not a good way to get low RR. If you're going to put that unrealistic limitation on yourself, then by all means go with the tubulars...they can't be any worse.
Of course, if you meant that you'd use "open tubulars" (i.e. clinchers with glued on tread like a tubular) then never mind.
In short, if you get rid of the silly tubular-clincher constraint, the "no-brainer" answer is definitely clinchers. If that constraint stays...do whatever you want since either way you'll be slow...or, at least, much slower than you COULD be.
Hope this helps! ;-)