SG-1 vs. XL-1 models

Hi all,

Here there is quite a difference in price (the XL-1 model being cheaper) between the Wiley X XL-1 and the Wiley X SG-1. Is the SG-1 model technically better, or is there only a difference in shape?

The specific models are SKU: 71 & SKU: 291. Both come with smoke & clear glasses.