In keeping with my doing nothing all day, here are some comparison swatches I did awhile back! (Read: I really didn't do anything today)
Essie Smooth Sailing and Finger Paints Grape Gumball are both blue-purple shades with chunky, almost glass-fleck-ish shimmer.
In this light, you really can't tell the difference between the two. I almost didn't buy Grape Gumball because they looked the same to me at first glance.
The differences are very subtle. Smooth Sailing is a touch more blue than Grape Gumball. They're not exactly the same, but if you have one and you're not obsessed with blurple like I am, you probably don't need both. The formula on both is similar, this is 2 coats each. There's a bald spot visible on my thumb, but that was more due to my application of it rather than the formula itself.