Qt 5.10.1, built for Windows with VS2013 and configured as

configure -debug-and-release -nomake tests -nomake examples -opensource -force-debug-info -opengl es2 -angle -qpa direct2d -icu

I see different QML animation time between Debug and Release builds:

• Debug builds are OK and timed near-perfectly (1000ms Timer lasts around 980ms)
• Release builds are significantly faster - 1000ms Timer lasts 680ms in average (varies in range between 660 - 800) on the first system and around 470ms on another.

This has been tested on 2 systems - one is NVidia Quattro K600 and another is Intel HD Graphics 3000.

Measurement code using QML Timer (green is a Text item):

    Timer {
        interval: 1000
        running: true
        repeat: true

        property double startTime: 0

        onTriggered:
        {
            if (green.visible)
            {
                startTime = new Date().getTime()
                green.visible = false
            }
            else
            {
                time.text = new Date().getTime() - startTime + " ms"
                green.visible = true
            }
        }
        }