Luisa, they are both recommended, but they liked the Sideswipe better. Here's what they had to say
It doesn't seem to be much difference.
From CI...
Stopping your stand mixer every few minutes to scrape down the sides of the bowl can be tedious, but two new products promise to do it for you (and mix ingredients at the same time): the SideSwipe Spatula Mixer Blade and the BeaterBlade+.The BeaterBlade+ offers a single beating-and-scraping “wing”; the SideSwipe has several angled silicone fins that beat, scrape, and push batter down in the bowl. While both models blended cake batters well and creamed butter in half the time of a traditional paddle (you may need to adjust recipes), it wasn’t until we mixed Spritz Cookies that we noticed the major advantage of the SideSwipe: Our recipe recommends stopping three times to scrape the bowl, but with the SideSwipe, we could add ingredients without stopping until the dough came together, leaving completely clean sides in the bowl. Meanwhile, the BeaterBlade+ left smears behind. SideSwipe makes attachments to fit KitchenAid stand mixers and a few other brands (check its website to match your model to a specific blade before buying).
SideSwipe Spatula Mixer Blade
The paddle has several angled silicone fins that beat, scrape, and push batter down in the bowl. When baking our recipe for Spritz Cookies, which recommends stopping three times to scrape the bowl, we could add ingredients without stopping until the dough came together, leaving completely clean sides in the bowl.
BeaterBlade+
This offers a single beating-and-scraping "wing," which blended cake batters well and creamed butter in half the time of a traditional paddle. However, when we mixed our Spritz Cookies, the BeaterBlade+ left smears behind.
