Great sponge for only $5.99+tax (CDN), I actually prefer this over the BB.
It's a fraction of the cost and applies foundation/concealer/powder just as well. Although it is marketed for highlighting and contouring, I use it for foundation & concealer. Obviously you can use it however you like, but that is the main purpose of how I use the sponge.
Size: Despite differences in dimension, the size of the RT sponge is very comparable to the BB, wet or dry.
Density: I find that the RT sponge is more dense than the BB. I personally prefer this as this allows you to really work the product(s) into your skin.
Blendability: Blends just as well as the BB sponge whether it is with foundation or concealer. I do not find that it soaks up more or less product than the BB.
Application: I use the flat large side for foundation and powder application. For concealer, and contouring, I will use the smaller angled flat side as it has a smaller surface area, allowing for better concentration of product(s).
I haven't cleaned the sponge yet, but I'm assuming it will be quite comparable to the BB.
Price: $5.99CDN...which I think, is the selling point of this product especially since I will be replacing a new one every couple of months.
I will most definitely repurchase this over the BB and recommend this as it does quite an amazing job for a fraction of a BB.