A lot of people are going to tell you a lot of things about goggles. In the end, you should care about two things
1.Do the goggles fit correctly
2. Can I see out of them properly
#1 - Fit. Fit doesn't just mean 'do they fit around my head'. You want a goggle that is
-Big enough for your face
-Big enough or small enough for your nose bridge (too small and you'll have problems breathing when the goggles are positioned on your face properly)
-Roughly matching the curvature of your face (othewise you will have gaps where the goggle gasketing doesn't seal against your head well enough
-Will fit over (or under, depending on how you wear stuff) your helmet, mask, or balaclava
#2 - Optics This just boils down to 'can I see properly'. I wouldn't pay any attention to 'spherical' vs 'cylindrical'. The refractive index of the plastic lenses is not enough to make a noticeable difference. Some people may disagree, but physics disagrees with them. After all, you are snowboarding, not shooting clay ducks at 100 yards away.
-Do you have a good, wild field of view or do the frames cut off important angles of vision
-Do they fog up quickly and take foever to de-fog (some goggles have venting adjustments to help with this)
-Are the lenses the appropriate shade I am looking for (I suggest 2 pairs of goggles instead of fooling around with switching lenses)
Most shops carry EITHER Smith or Scott. I've never been to a shop that I saw carrying both of those two brands. Of the shops that do carry Smith, most of them say that Smith tends to sell a little better. Most people I go to the mountain with have Smith, Oakley or Anon goggles. Remember, brand is less important than fit & function. Make sure to try on as many pairs as you can and try to determine the differences you can feel.... (which admittedly, is hard to do until you've worn goggles for a bit).
I'll have to disagree with you on that Spherical comment. The difference between a spherical lens and a flat lens is night and day. It's not about the material (plastic). It is about the manner in which the lens is thinned. I'm not saying flat lenses are going to ruin your experience (at least at your local hill, can't speak for backcountry), but once you ride a few times with a spherical lens, you won't want to go back to a flat lens.
I also disagree with your comment about shops carrying either Smith or Scott, but not both. I can only speak for Michigan, but I see both Smith and Scott regularly. The company I work for owns 7 brick and mortar shops and we carry all major brands. Scott beats Smith on for their entry level flat goggles, but Smith outsells Scott's spherical thanks to the I/O and I/Os.
Another thing to consider with buying spherical is the anti-fog. Since spherical goggles are more expensive, they utilize better anti-fog technology. Take Smith for example. They burn the anti-fog coating into their spherical lenses. Their flat lenses just have basic coating. Along the same logic, the more expensive spherical series goggles will have a much better design. This means better ventilation to further fight condensation and fog.
Goggles are definitely not created equal. Spherical is superior to flat for many other reasons than just the curvature.