I'd hope riders consider today a better option to attack than tomorrow because of the flat after the Marie Blanque.
Oh, today is definitely the better option to attack - the last two climbs chain together much better and there's a descent practically all the way to the line so no real concern of needing any energy left afterward.
The flip side is that Marie-Blanque has steeper ramps than Peyresourde and that every rider knows pretty much every inch of the Peyresourde,
Since yesterday was raced harder than any of the GC guys would have liked (especially those that lost time of course) that could be a good factor for today (more vulnerable people who are less fresh than they would have been) or it could be a stifling factor (unwilling to risk the legs or work the team from too far out in fear of being isolated later). I don't think we'll be able to really determine that until Port de Balès. And I think most of the big gun teams should try to get somebody in the break, except maybe Jumbo and Ineos but even them I think ought to do something to that effect. For Ineos that would be ideal if Sivakov can make it there, as he's obviously been struggling all week, they could make use of him if they catch him on Balès or Peyresourde whereas if he'll be in the péloton and tailed off as he just tries to make it through to the rest day, obviously they can't really factor him into their tactics for the day.