First let's talk about the Missha BB Boomer. When I squeeze the product out, there's definitely a pearl finish to it. Applied, it gives the face a slightly dewy finish. The face also become slightly sticky (to help the BB cream stick better I suppose).
#13 doesn't have the gray-ish beige cast that #21 does so it gives off a "brighter" quality as you can see. Blended in fully, the colors don't differentiate too much. #13 seems to be a tidge too light for me still though so I'm working through #21.
The Missha M BB Boomer I don't think I will purchase. It just doesn't seem like something that improves the finished effect that much. This would be good for those with oily skin (need something to give BB cream extra hold).
If you haven't already, check out my review of No.23, which also has time-wear comparisons.
On a sidenote, I have so many pictures/ swatches of products to be reviewed but I never get around to them for some reason, haha. slowly but surely.