Rothy's and Allbirds have a lot in common. Both founded in 2015 in the San Francisco Bay Area, the startups quickly became popular in the area for their practical and sustainable approach to footwear and gained the funding to prove their future potential. They've also found an audience in East Coast cities like New York, where the culture of walking makes the search for cute and comfortable flats even more dire. In addition to women's flats, Rothy's sells loafers, sneakers, and kids' shoes. While Rothy's is best known for its flats, Allbirds is best known for its sneakers, and flats are a brand-new foray into non-sneaker styles. It makes men's and women's wool and eucalyptus sneakers, as well as children's wool sneakers. Read more: 11 San Francisco-based clothing startups that prove New York City isn't the only capital of fashion Rothy's makes two different flat styles: rounded toe flats ($125) and pointed toe flats ($145), letting you decide between a versatile, everyday flat or something better suited to polished occasions. They come in a variety of neutral and bright colors, as well as flashy prints such as a spotted leopard print. These colors and prints rotate out from time to time, so there are always new ones to choose from. The colors of the insoles depend on the style — sometimes they match the uppers and other times they don't. You can also buy extra insoles in different colors here. An easy way to identify Rothy's flats are the blue stripe at the heel of the shoe and the knit fabric. Both flats have an angular, V-style opening, which can help your feet look longer or more slender. Allbirds makes one flat style, the Tree Breezer ($95), currently available in four colors. Allbirds has a history of releasing limited-edition colors quite often, so check its site, social media, or the Insider Picks page to find the latest options. Its flat has a rounded toe and rounded opening, with a mesh knit fabric that's more noticeable than Rothy's. The collar of the opening is also more obvious and is made from a ribbed knit, so it hugs your foot more closely. The insole is Allbirds' standard gray insole. Both companies pride themselves on using sustainable materials to make comfortable shoes. Conveniently, both their shoes are machine-washable (but take the insoles out first), making it easy to keep them in top shape. Rothy's construction: Uppers: 3D-knitted fabric made from recycled plastic water bottles. As of this writing, Rothy's has repurposed more than 30 million water bottles. Insoles: Recycled plastic water bottles and recyclable foam Outsoles: Recycled, carbon-free rubber Allbirds construction: Uppers: Knit fabric made from sustainably harvested eucalyptus pulp Insoles: Merino wool and castor bean oil Outsoles: SweetFoam made from Brazilian sugarcane Both companies' flats are light, really comfortable, and made for all-day wear — we wouldn't be writing about them if they weren't. Thanks to their unique designs, however, they do feel comfortable in different ways. You can get both Rothy's and Allbirds in half sizes (a first for Allbirds). Rothy's fit true to size, but if you have wide feet or fear toe crowding in the pointed flat style, you should go up half a size. They mold to your foot and are breathable, with slight give so you can still wiggle your toes around in them. They're great for summertime wear since they stay slick and dry. I've been wearing and washing mine for nearly a year and they don't stretch out. Allbirds recommends going up half a size for its flats, which tend toward a more snug feel. The cushioned insoles are supportive, and the overall feel of the flat is softer and thicker than Rothy's. If you plan on being very active, you might like Allbirds' flats more because of the aforementioned collar that grasps onto your foot. Rothy's rounded toe flats retail for $125 and the pointed toe flats retail for $145. Allbirds flats, like all Allbirds shoes, cost $95. If you don't want to spend more than $100, Allbirds are the obvious choice, but there's the trade-off of fewer color and print options, not to mention the fact that they tend to sell out more quickly. If you're willing to spend $30 to $50 more for Rothy's, you've widened your options and are likely to receive your shoes more quickly. $100 is probably more than you're used to paying for a pair of flats, but sustainable clothing does tend to be more expensive, and both brands' shoes are durable and well made. We love both Rothy's and Allbirds flats and wear them often. If you're already familiar with the feel of Allbirds sneakers and like that, you should go with the Allbirds Tree Breezers. They're soft and cushion-y, with an almost sock-like feel and the added plus of an under-$100 price point. However, if you want more color and print options and a less cushioned (but still comfortable) feel, try one of Rothy's flats. Shop Rothy's Flats here and Pointed Flats here. Shop the Allbirds Tree Breezer here.