Thicker rads should make the difference but they won't. Larger radiators are better for cooling than smaller (thicker) rads.
I think jayztwocents did a video on it a while back. A same sized radiator one thick one thin and there was overall only a degree or two difference between the two.
I would for sure go for the 2x360mm radiators. They will offer you the better performance.
Its a tricky one and fpi and make of rad and choice of fans come into it as well.
Thicker rads dissipate more heat than thinner ones. full stop. Especially if the fan speed is increased however at low fan speed there is little diff or even zero.
Yes it might only be one or two degrees difference between a thick and thin rad but equally its probably the same going from a 280 rad to a 360 rad.
Here.
http://thermalbench.com/2015/01/05/hardwarelabs-nemesis-480gts/5/
difference between a fat and thin hardware labs nemesis is zero degrees delta at 600 fan speed. At full fan speed its one degree delta
There is more difference between choosing different rads then there is in the thickness of them though.
So I will adjust my first post. If going for silence and low fan speeds, surafce area of rads more important than thickness so 2 x 360 > 2 x 280.
If going for higher fans speeds and best cooling then 2 x 280 thick > 2 x 360
In the middle fan speed, probably nothing in it
Just go for as many rads as you can fit