Reflection: Whats the difference. Fresnel Tick or Falloff map?

[Morne]

Hi all

In VRayMTL next to reflection there is a check box "Fresnel". What is the diffrence between ticking this box or applying a falloff map in the reflection texture?

[^Lele^]

for the same IoR, unless you touch up the map curve, none afaik.