I have a number of pocket bins, including the Zeiss 8x25 Victory and the Leica 8x20 Ultravid BL. Actually, I have two of the latter because I like it so much. The Leica (especially the BL version) is more compact than the Zeiss when it is naked, but in its Leica leather clamshell it is the same pack size as the Zeiss in a simple cordura case. Since I usually carry the Leica in its case, I don't find its smaller size to be of practical consequence. I find the color of the Leica _slightly_ more pleasing; it has more touches of red, versus more of a blue-green to the Zeiss view. The Leica also seems to be more contrasty between highlights and shadows, which looks nice, but I am not sure it actually so good for getting diagnostic views of birds in dappled light situations. Both perform against the light quite well, but I would say the Zeiss is superior overall. CA is not a problem in either. The focus knob of the Leica is superior to most pocket bins in its accessibility for rapid manipulation, but the Zeiss is even better, and it operates more smoothly. As far as FOV, ease of view (popping up to the eyes and seeing without fuss) and getting on the bird quickly, the Zeiss has no equal amongst 8x20 and 8x25 bins. For me, it is really something special and has made my 8x32 bins obsolete for birding. So, although I really love the Leica in many ways, the Zeiss just kills it for overall birding functionality. Consequently, I always use the Zeiss these days. I had them both out last weekend, and I do love those little Leica which served me faithfully many years, but I just can't deny that the Zeiss crush them when it comes to birding tool performance.
--AP