Paul,
Eneloops are rated at a minimum of 1900 MAH. Most alkaline batteries are around 2500 MAH. But the voltage on alkaline cells  drops faster. Thye also are pretty bad for  anything that draws much current.
Often the NiMH batteries actually last longer in any given application.
http://www.greenbatteries.com/battery-myths-vs-battery-facts-1/#:~:text=For%20example%20AA%20alkaline%20batteries,or%20four%20times%20as%20long.

"Battery capacity ratings are meaningless when used to compare different types of batteries or to compare the capacity of batteries powering different types of devices.

This means that you may not be able to predict how long your electronic device will run just by looking at the capacity rating of a battery. For example AA alkaline batteries typically have a capacity rating of over 2,500 mAh and AA NiMH batteries have rated capacities of only 1,200 to 1,900 mAh. But when it comes to actually powering an electronic device like a digital camera, the NiMH batteries will often run the device for three or four times as long.

(for an explanation see Battery FAQ, Why do my alkaline batteries run out so fast?)"

This is just something I found in a quick search. Lots more info is out there if it is of any interest to you.