Hello & welcome to the forum!
In reading Apple's description of battery life (
HERE), the three current models are described similarly, but I suspect the iPad w/ retina display (different processor & 4x the pixel resolution of the other two) would likely be more 'battery hungry'; BUT, your battery life is much more dependent on 'how' you will use the iPad (e.g. music, surfing, videos, intensive gaming, radios on, screen brightness, etc.) - if you REALLY want to know more specifics about your battery, especially relative to your settings & activities, then I would suggest adding a battery app - I have
Battery HD+ - the attached screenshot shows my current status and the hours estimated for certain activities (standby is much longer than reported by the iPad in settings - not sure why?) - hope this helps. Dave