In reply to cathalb55:
As you say, fit is vital. Can also look at weight and insulation. A lighter boot can feel more precise, especially when mixed or rock climbing and can be less tiring - assuming it is still supportive enough. However, it may lose out on the insulation front. If you are standing around a lot, get cold feet, intending staying high (4,000m plus ) for long periods of time or thinking about alpine winter then a more insulated boot may suit. It rather depends on the routes you currently want to do and intend doing over the next few years. No one pair will do it all, you will probably aim for compromise in one aspect or another.
I feel the boots with built in gaiters lack flexibility for me, often I don't need gaiters or only very lightweight ones. So having no built in gaiters lets me add gaiters when I need them. There is a boot hire service available in the UK and many alpine regions which gives you a chance to try different boots out.
Personally, I currently use Nepal Evo Extreme GTX. They are light, cope well with easier alpine / UK days and lots of walking / scrambling but are also great for ice / mixed and alpine summer. However, they are not so well insulated and their life span is less than some heavier and more robustly built boots.
