The sponge retails for $5.99 which is the biggest reason it's so popular compared to the beautyblender. There are some obvious shape differences between the two. The beautyblender is more egg-shaped, with a full bottom, while the RT sponge is fullest in the middle. It also features a flat edge which is supposed to help get into the "contours" of the face. I find that this flat end doesn't work well for me and makes the sponge more difficult to hold. Both feature a pointed end however the beautyblender has a finer, more tapered point.
I use both sponges wet and I've definitely noticed a difference in how they retain water. Both swell to double the size but the beautyblender seems to retain almost no water. The RT sponge, unfortunately, is too porous meaning that it holds a lot of water. This also means that it sucks up A LOT of your foundation. I probably use twice as much with the RT sponge. The RT sponge also feels heavy in comparison to the beautyblender, and has a more springy feel than the softness that the beautyblender has. Both give a nice, airbrushed finish, but I really do think the beautyblender's is more seamless and natural-looking.
While the Real Techniques Sponge is far superior to a normal makeup sponge, I still think it's pretty far behind the original beautyblender. If you're not willing to shell out $20 per sponge it IS a good dupe, but the beautyblender is still my top choice. Sorry wallet.
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