shortest loop always win.
in a single loop, the water temps will usually stay value in equalibirum unless u have an obnoxious amount of heat load / high restriction.
(~300W of heat required for water to go up 1C @ 1gpm.)
So again shortest loop wins, because there is no imaginary temperature gradient ur expecting unless again... you have very weak flow, or very hot chips.
I would..
Res -> Pump -> 240 rad -> GPU -> CPU -> 360 rad -> res.
Which would be your shortest loop.