FFRR Active Locking Rear Diff - specify or not?

[LooneyTunes]

In the process of speccing a FFRR and wondered if anyone had any practical experience of the locking rear diff?

It’s standard on the 4.4 v8 diesel, and the 565hp supercharged petrol but seemingly not on the 525hp version... for mainly road + light off road (wet grass) is it a box that I should really be ticked?

Any experiences/thoughts appreciated!

[LooneyTunes]

Decided to add it... there will be much amusement if I get stuck on a field in a £100k+ car, so for £500 I might as well reduce the chances of that happening.