Smith Goggles are worth what you pay for them. I've been rocking smiths for years and have come to rely on their fog free clarity, leaving many a buddy in the dust scraping and wiping goggles while I take his line.
The Fuse has a flat lens - curved on only one axis instead of two like a spherical lens (hence sphere). I have enough goggles, definitely one pair for any kind of light, but I just bought a pair of I/Os anyway. They are awesome. Definitely worth it. They fit perfect with a Smith helmet. The Fuse was my go to goggle for a long time and I still love them, but the spherical lens is far better, not sure how old yours are but the new version of the Sensor Mirror lens (included as an extra with the I/Os) is the BEST lens around. Has a great mirror, most people won't see your blood shot eyes, but it lets in tons of light for flat light days and storms. 70% Visible Light, almost as good as a clear lens at 84%. Plus Smith came out with a silver mirrored lens that is much better then their older Platinum Mirror its called the Ignitor Mirror.
The I/Os are made on a similar line as the Phenoms which have a great med fit. The two lenses that comes with I/Os makes good sense when you compare to a similar one purchased with a spare lense.
Sorry for how long that got, guess I like smith more then I realized.
