In reply to TobyA:
Wasn't the "best practice" i.e. what the Glenmore Lodge folk suggest changed a couple of years back to everyone might as well use 50? Something to do with better for braking? There were some article about it as I remember.
Probably rather longer ago than that - they were certainly recommending 50/55 when I did my winter ML, which was probably 10 years ago. Certainly before kids, and the oldest is 6.
And yes, it was about being able to get a good braking position - with lower arm/hand both strong (elbow in by side) and covering the nasty spikey bit on the end. Assuming this leaflet is current, they seem to have backed off a little - this says between 50 & 75...
www.glenmorelodge.org.uk/cust_images/pdf/mountainsport%20articles/Glenmore%20Lodge%20Dec.pdf
Here we go, this is worth a read - both sides of the debate in a proper spat
www.traditionalmountaineering.org/FAQ_IceAxe.htm
Personally, I'm happier with my 50cm axe than my old 65cm one. Probably depends if you like using it as a walking pole, which I have to say I rarely do. Or if I do, I'm lent over into a hoolie and 50cm is quite long enough!