My opinion.....
There are a few "truths" that I have learned over the years from trying and buying an uncountable number of models. One, an 8x30 is going to have a larger field of view than its 8x40 counterpart. There are exceptions of course but because of the optical design itself a 30 mm model typically has a wider field of view than a 40 mm model. If the 40 mm model has the same or greater field of view then it is typically because the manufacturer created the 40 mm first and put all of their effort into designing that configuration as they thought it would be their best seller.
Having said that, I would assume that an 8x30 of the same design would have a more well-corrected view, in terms of aberrations and distortions. The Yosemite, in this case, is a very simple design. Because of it being simple there is less chance of there being more optical issues with it. The Legacy, on the other hand, has a wide field of view for an 8x40-something model. Since it is relatively inexpensive that usually means one of two things. Either a) it has a simple eyepiece design which then leads to short eye relief (a result of trying to achieve a wide field of view in a low cost instrument) or b) it is going to have a great deal of optical aberrations or distortions in the image.
Basically, at the low price points, there is only so much you can do with the optical design. Since the Yosemite is a simple design in an 8x30 configuration you are likely to get better overall optical performance.
Further more, the Yosemite has only been around for maybe 5 or 6 years....and it has had at least one "upgrade" in terms of design. Because of this I would expect it to have the latest coatings. The Legacy, on the other hand, has been around for much longer and I don't ever remember reading anything to suggest that the current model is any different than the one I sampled 8+ years ago.
Hope this helps a bit.