Some 1A chargers don't actually manage to output 1A (if this happens, the tiny white charging LED on Mojo will flash/blink, which indicates that charging is NOT happening)
However, if the LED illuminates continuously, all is well.
As long as the LED illuminates continuously, you can you either of the chargers you mentioned. It doesn't really matter, although you might find the 2.4A charger charges Mojo slightly faster (you'll have to try, to find out).
Mojo has quite a lot of protection and regulation on the charger input, so you will not be able to charge 2.4x faster, though!
Yeah I remember rob stating that Mojo draws 1.9A max so no need to worry about 2.4/2.6/3.0A chargers.