I can comment on the 8x30 SLC and 8x32 EL, which i have and use, and the 10x42 SLC and 10x42 EL which i have examined closely.
The bodies differ and the weight and handling differ as well. ELs are a bit lighter, handle better, and focus closer.
The two lines are similar, but not identical optically. ELs are a bit brighter, more color neutral, have less color fringing in bright light, work better when looking into backlit objects (as in searching for deer at the base of a hill when the sun is setting behind it), and have slightly more distortion at the edge of field of view.
The SLC work just as well in poor light and dark weather, but have more flare and less contrast when looking at backlit objects. They work well, though. They also are just a bit less bright and less color neutral, they show colors with less vividness than the ELs, especially in sunlight. They have a wider "sweet spot" free of distortion at the edges.
The differences are small enough that you probably would not be able to see them inside a store. I've used both extensively in the field, and i can tell you that the SLC line is all you need for hunting.
If you will hunt the open spaces in the west and handshake and handholding are not a problem, go for the 10x42 SLC. If you will need low light performance to check foodplots in the dark, go for the 7x42. If you want both in a smaller package, go for the 8x30 SLC.
Despite it being small and having a smallish focuser in an odd place, the 8x30 works very well with gloves and in low light and dark weather. During November hunting, my SLC 8x30 works very well with excellent brightness and contrast about 35 minutes before sunrise and 35 after sunset.
One more difference: the focuser on the EL does get stiffer and harder to operate in the cold, the one on the SLC does not appear to.