I'm no expert on them, but I did notice a slight difference when I compared the 2 brand new. Not being a fan of the grips on the Shadow anyway, and liking the look of the 75 more, I bought the 75 Shadowline. If you've found a SP-01 Shadowline I'd say get it as they are very few and far between.
I can tell you that this is one incredible pistol, even out of the box. But being a new shooter, I don't know if you'll notice the difference until you've shot it a lot more. I'd say go with whatever one feels better in your hand for a start. That being said I put the Hogue grip on mine (big hands) and I've never held a more comfortable pistol.