picking a charger

When picking an ac charger UK

I am aware that things do make lots of difference in terms of charging rate

So for charge speed what is more important amp hour or wattage

Or is it a combination of the above

If the wattage makes a fair bit of difference then is there a app that will tell me the max wattage of my current chargers as wattage is never displayed

I ask mainly because I have known a 1amp an hour to charge quicker than a 2amp hr

I am using android

Thanks