Given the microfin coverage of the Eisblock XPX and the flow distribution design I think you're looking at most a 2°C difference similar to what was seen in xtremerigs' review with "Goofy" orientation on i7-5820K.
In a normal orientation the flow is inlet at left and the outlet at right but that is moot due to the flow distribution channel and jetplate. It's supposedly to increase performance at low flow operating points but I think it's not really as effective as claimed flow-wise.
"Flow at minimum pump speed"
EKWB supremacy Evo 73 L/h
XSPC Raystorm Pro (similar to Neo) 72 L/h
Aquacomputer Kryos Next 71 L/h
Eisblock XPX 64L/h
Heatkiller IV Pro 62 L/h
"Temperature difference between water and CPU"
Eisblock XPX : 23.6 Kelvin @ 64 L/h
Aqua Computer Cuplex Kryos Next : 24 Kelvin @ 71L/h
Heatkiller IV Pro : 25 Kelvin @ 62L/h
EKWB Supremacy Evo : 27.7 Kelvin @ 73 L/h
XSPC Raystorm Pro : 28 Kelvin @ 72 L/h
Even with R5 3600 and Eisblock XPX this person was topping out at around 65°C in Prime95 Small FFT , though gaining around 150MHz over stock cooler due to the drop in temperatures
When US-based Optimus watercooling launched , they claimed to be the first to 0.1mm channels (100 microns) and 0.125mm fins (125 microns) while the blocks designed in Germany generally are 200 microns. Swiftech is at 125 microns for their fins on the SKF series (including the cheap $50 LT model).
I believe the most important factor is fin coverage (are there fins over the cores?) and the fin density/height (how much of the heat is going into the watercooling working fluid).