In considering these pictures, it's important to think about the kinds of situations where a long telephoto is needed. Seagulls are extremely domesticated and have little or no fear of photographers, so it is easy enough to get close enough that even the 10:1 is overkill. But try to get close to a sparrow and you'll not have much luck.

From a print point of view, the bottom line would appear to be to avoid using the digital zoom if you can because of the lowering of quality. But even that advice should be taken with a pinch of salt. Some subjects just won't allow you to get close enough. Sometimes a bad-light situation can be overcome by narrowing the area of interest. If you know you're going to be reducing the image in size before printing, then perhaps on-location shooting advantages override the pure quality issues because when you reduce the size of an image in Photoshop, you can improve its sharpness and eliminate some of the problems that the full size image might have.