Q:

When I use <ui:inputEmail I get one thing.  When I use <input type="email" I get another

If I use this code for my input box to take an email address: 
<input type="email" onkeyup="{!c.sendSearchKeyChange}"/>

The event sent to sendSearchKeyChange has a prototype of KeyboardEvent.   And, most important to me, I can say event.target.value, and find out the value of the input box. 
If I code the input box like this: 
<ui:inputEmail keyup="{!c.sendSearchKeyChange}"/>

The event sent to sendSearchKeyChange has a prototype of just plain Object.   And event.target.value is undefined. 
I thought the keyup attribute supported by  just went straight through to the same place the onkeyup attribute goes to on the regular html element, but I guess not.   Is the event that is sent documented somewhere? 

(After getting an answer suggesting how to code it.) 
Actually, when I define a data attribute like this:
<aura:attribute name="thePhoneNumber" type="String"/>

And set up my input element like this:
<ui:inputPhone aura:id="phone" label="phone" placeholder="123-456-7890" 
               value="{!v.thePhoneNumber}" keyup="{!c.sendPhoneKeyChange}"/>

And have my controller like this:
sendPhoneKeyChange: function(cmp, event, helper) {
    var target = event.getSource();
    var theValue = target.get('v.value');
    console.log('theValue', theValue);
    theValue = target.get('v.thePhoneNumber');
    console.log('theValue', theValue);
    var myEvent = $A.get('e.c:PhoneKeyChange');
    myEvent.setParams({searchKey: theValue});
    myEvent.fire();
}, 

I get an undefined for theValue, whether I use v.value or v.thePhoneNumber.   I don't know why.  

A:

To perform what you are trying to do, you just have to make these modifications to your code:
<ui:inputEmail keyup="{!c.sendSearchKeyChange}" updateOn="keyup"/>

({
    sendSearchKeyChange : function(component, event, helper) {
        var email = event.getSource().get("v.value");
    }
})

some reference here:
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/aura_compref_ui_inputText.htm
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/js_client_side_controller.htm

