@ OP your reasoning is clear. The other advantage you can look for is water leaving radiators at a higher point than where it enters, as this helps avoid trapping air in the system and so makes bleeding easier. That's also how you've drawn it.
The usual mantra is that loop order doesn't matter, as it all ends up the same temperature anyway. There is a temperature drop across radiators and a rise across the cpu block, but it's fractions of a degree. Minimising bends and length of pipes to reduce pressure loss is probably more beneficial. If instead you want to go pump -> radiators -> cpu block -> reservoir then fair enough, thermodynamically there's a slight advantage.
In contrast, I believe there is a (fluid dynamics) advantage to placing the cpu block immediately after the pump, but I would attribute this to the flow immediately out of the pump being very turbulent. Given a long distance flowing down a pipe, the flow will reach a (probably still turbulent) steady profile. I would rather send the swirly, messy flow into the cpu block (which is usually designed to increase turbulence further) than a relatively clean, stable flow.
So, there is an argument for block first (turbulence) and one for block last (temperature), where neither effect has any realistic chance of being worth a degree centigrade. Still, I hope that made for slightly interesting reading regardless. Plumb it in whatever order takes your fancy
