Mount them up on the 808 and measure the widths. I suspect the GP TT will be quite a bit wider. That likely means the GP4KS2 is more aero. With the GP TT having lower Crr it is compromise. If you are heavier then maybe Crr is more important. If you are lighter or averaging higher speeds then aero may be the deciding factor.

TomA's Win tunnel wheel and tire testing demonstrated that very low Crr tires like the Spec Turbo Cottons still end up faster, in aero and Crr aggregate, than more aero tires that don't roll as well. The GP TT has similar Crr to the Turbo Cotton.

If you look at this and do some reasonable assumptions, I think it suggests the GP TT is the way to go.

My main reasonable assumptions are:

1) 23mm GP TT is aerodynamically similar to the 23m GP SS.
2) The 22m Attack is aerodynamically faster than the 23mm GP4KS. Or at least a wash.

Also stipulate (with some good evidence) that the GP TT is effectively equivalent to GP SS in Crr, and the Attack is effectively equivalent to the 23mm GP4KS in Crr.

Then looking at that graph, it really suggests go with the GP TT.