Here are the main differences between Spherical goggles lenses vs. Cylindrical lenses (also referred to as flat lenses). Cylindrical lenses appear to be flat vertically, but curved horizontally around your face. On the other hand, spherical lenses are curved on both vertical and horizontal axis, so they appear to look more like a bubble or a contact lens.
Spherical goggle lenses have a better optical quality, and usually a larger interior chamber volume in the goggle, which can help prevent fogging of the lens. Typically, spherical lenses are mold-injected which allows for the full lens tapering, which means the lens is thicker at the center and gets thinner at the edges. Lens tapering allows for peripheral light to travel the same distance to your eye as light coming from the center, which results in a better performing optical lens. A spherical lens creates less distortion and less glare, but spherical lenses are more expensive than cyclindrical lenses.
Cylindrical goggle lenses due to their flat shape, will have a lower profile, thus have less interior volume, which may lead to more lens fogging. Due to the flatter lens, a cylindrical lens might have more glare and create a bit more distorted view. These are the why goggles with cylindrical lenses are typically less expensive than a spherical lens.
Here are a few of highly rated Spherical Ski Goggles:
Here is one of the best Cylindrical Ski Goggles: