The one from Amazon looks like a great scale.
The two scales are a perfect example of the trade-off between upper and lower end precision -- at least for any scales I can afford. The rule of thumb I was taught is that you want a decimal point of measurement beyond what you expect to weigh. i.e.: If a recipe calls for 5.5 g of doodlebugs you'll want a scale that measures to 5.50 grams. I have two scales that have almost the same ranges as the two you have here. I almost never pull out the 0.1 scale. I just don't have the room for two scales out and the work-around isn't a big deal. If I need 150 ml (grams) of water, I weigh out the water in a couple of divisions.
Important, though: You'll want a calibration weight, or even better, a set of them. The instructions for calibrating the scale will be included with your model. It's very easy, but very important.
Re: contact printing under glass. It can be done. It will be fine in the beginning as you're learning and deciding if all this is something you really love doing. But, in the long run, especially with handcoated paper that isn't dead flat when it dries, the tight contact afforded by a good spring-back frame can't be beat.
btw: excellent questions!