There are none, as PNG's are lossless. However in production, I would suggest EXR's. PNG may not lose quality, but what about size? Is it smaller, bigger, equal to TGA or TIFF? The PNGs are quite big in size, as the rendering of my solar system has proven, but I didn't bother to check TGA size. All i know is that TGA was giving me transparent bg problems, as AAE was putting a fake background, so I needed to switch to PNG.