Great question boss!!!
Well for me this is a no brainer, the obvious choice is your wife. No matter how much you love your mother, no matter all the things that she went through in life to raise you, the choice you should make should always be your wife.
The thing is, your mother is the one that brought you into this world and raised you, but it's your wife that will bring your own children into this world. If you deny your children the love and care of their mother then what right do you have to even save your own mother.
Unless your wife is a terrible person who is hated by everyone in your family, I don't see any reason why your mother would even say that you should save her over your wife. In life, when a man gets married, he leaves the house of his parents and moves into his own house with his wife and starts his own family. From that point on, his first duty is to his nuclear family.
You can't ask for a girls hand in marriage, make her leave her father's house then choose your mother over her, it doesn't work that way. The choice might be a little difficult to make if you just recently married your wife and you don't have any kids, but as long as there are children involved then the decision should be relatively easy.
Even your mother will probably advice you to save your wife, I mean like what mother wouldn't be willing to sacrifice for her child. To me, if it was my husband or my dad, I wouldn't think twice about it, I'd save my husband.
There's also the fact that your parents are old and have actually lived life, no one wants to die but a person who has a kid that's gotten married has probably lived to a reasonable age and I think that's enough for you to know who to choose.