Things we consider before we buy an axe for sale at AMH are:
Weight is fairly self explanatory but their is a relationship to durability and strength that must be considered. We really like the Nepal Light at about 9oz but we mainly use it for fast and light mountaineering when we are unroped or roped for glaciers but we are not comfotable with it for belaying with as an anchor. On the opposite end of the spectrum is the Arc Light. At over 26 oz it is the heaviest axe we carry and most of us don't use it but if you were to bet your life on the stregth of an axe this is the one to bet on. Most of us have chosen something between the two for even big mountains.
A mountaineering axe is gripped by the head more than any other position and if it is uncomfortable it can be miserable.
We like an adze that does not droop much. With minimal droop the axe is more comfortable and chops ice with a more comfortable swing. Some axes have a steeper droop which works better in slushy or rotten ice when used like a pick.
The pick is sometimes a point of contention. Negative clearance, positive clearance and angle of the pick to the shaft. A positive clearance pick essentially has more of a point to the end of the pick. Supposedly you have a greater chance of the pick being ripped out of your hand during a self arrest with a positive clearance pick. A positive clearance pick also penetrates the ice better. A negative clearance pick will self arrest more gradually but does not penetrate the ice as well. A negative clearance pick can be made positive with a file. A positive clearance pick can be made negative but it will shorten the pick. The less the angle of a pick to the shaft the more technical it is but not as good for chopping.
As far as self arresting goes, it is very hard to self arrest on terrain that needs a pick to do so (ice and bullet proof snow) unless you do so almost immediately. It is unlikely the pick will make the difference between life and death - your reaction will.
The spike is best if it does not work at only one angle. That said the Air Tech Racing is one of out favorites and its spike must always be angled in one direction to work. A price some are willing to pay for the weight savings.