DO NOT BELIEVE IT! . . . the wind statistics are highly inconsistent and the word "prevailing" is open to mis-interpretation - just accept that on some days it'll be behind you and others it will be head-on.
There are also the wags that suggest JOGLE is easier because it's downhill . . . you can put them right on that: On an absolute net basis LEJOG is downhill - you start on the high cliffs at LE and finish almost at sea level at JOG. Of course, the total climbing, for whichever direction, will be dictated by the route.
Having ridden both ways, on almost the same route:
JOGLE - despite Scotland being seemingly more mountainous it was a much easier start - the hills are long drags rather than the sharp rises in the SW of England. By the time you reach England you are well towards half-way and into the swing of riding good distances day-after-day ... by the time you reach Devon and Cornwall with the real hills your legs are ready.
The logistics of getting to JOG are simpler for most people (see comments about trains)
Cycling south, in theory, will mean that the weather improves and for me, the countryside and a few more people around in the SW made it a more pleasant trip.
LEJOG - the steep hills start straight away, perhaps before your legs are really ready for them. The further north you travel, and into Scotland the wilder the country becomes in terms of scenery - towns and villages are fewer . . and the risk of poor weather increases. The last 100 miles or so are pretty barren, although scenery is stunning in its way - it's likely to be very windy ... and arrival at JOG is a bit of an anti-climax for many. There's not much there!
Summary : If it's your first time I would recommend JOGLE - it was easier to ride than LEJOG (although for LEJOG I was 5 years older, and we took about 4 days fewer!)