This was tested in Google Chrome v. 18.0.1025.168 if that matters :)

Using this code:

$(document).on('hover', '.item', function(event) {
    console.log(event);
    console.log(event.type);
});

On mouseenter it shows:

Output from event:

jQuery.Event

...

toElement: HTMLImageElement

type: "mouseover"

...

Output from event.type:

mouseenter

On mouse out it does:

Output from event:

jQuery.Event

...

toElement: HTMLImageElement

type: "mouseout"

...

Output from event.type:

mouseleave

When trying to catch the event, it only responds to mouseenter/mouseleave and not mouseover/mouseout.

Example, this runs console.log():

$(document).on('hover', '.item', function(event) {
    if (event.type == "mouseenter") {
        console.log('Success');
    }
});

while this doesn't:

$(document).on('hover', '.item', function(event) {
    if (event.type == "mouseover") {
        console.log('Success');
    }
});

You can send me an email if you have any further questions.