Quite easily. It uses a long flue path to extract the heat down to an effkux temperature up the flue of about 35C.
With CH water running at higher than that, even in a codensinng boiler, more heat has to go out of the boiler flue than the aga flue.
The ONLY thing that marks boiler efficiency is how hot the exhaust gases are when they leave the house and go through the insulation.
That and the initial combustion temperatures, which are fairly similar in both cases.