TO ANSWER ALL THE QUESTION:
mah is miliamp/hours which means the higher the number, the longer the battery last
nimh batterry last much longer than nicad or alkaline battery in high drain device such as: digital camera, portable audio player, etc.. and environmental friendly. minh is almost memory free and that why they discharge much faster even when not in use to protect the battery.
nicad is no good for alsmost everything and not env. friendly, very toxic. however, for r/c car and plane, nicad is the choice since the energy flow (voltage) is much higher than nimh --> car/plane run faster but last very short time.
alkaline is a waste, only use them unless you really have to. use for emergency device only such as dectector because they retain their charge much longer than nicad and nimh. use alkaline rechargeable battery for these thing.
alkaline and nicad contain very toxic material and require special treatment before release to the envir., but i never seen anybody take time to dispose them properly, so please use rechargeable batteries.
i am waiting for lithium ion to come out, but its will be a long time since nobody embrace the technology because all the big bad company like duracell and energizer want to make money on alkaline, and try their best to keep people away from using these technology.
just my .02cent