Using a WLF is a matter of getting used to the right/left inversion. After a while you learn to move the camera in the opposite direction of what you'd think by looking in the WLF. A prism finder eliminates that issue, usually has a bit of magnification and you can add corrective diopters. But it comes at the price of being heavy (quite heavy) and expensive. The WLF will have a pop-up magnifier that gives greater magnification than the prism finder, so it can be more accurate for checking focus. And the greatest advantage of the WLF is since you are not holding the camera up to your eye, you can have eye contact with the subject, something that often leads to better portraits. The depth of field issue has nothing to do with the finder, but the longer focal length of medium-format lenses. Most MF SLR's (including your 6008) have a depth-of-field preview button allowing you to judge that. TLRs do not.