Azahar vs Folium
Folium is a paid 3DS emulator for iPhone and iPad, available through the App Store as the first commercial 3DS emulation option for iOS. Azahar is free, GPL-3.0-licensed, and runs on Windows, macOS, Linux, Android, and (via RetroArch) iOS and tvOS. For anyone on a platform other than iPhone or iPad, Azahar is the natural choice.
Folium is iOS and iPadOS only. Azahar covers Windows, macOS, Linux, Android, and iOS and tvOS via LibRetro cores in RetroArch. If you want to play 3DS games on a PC or Android device, Folium is not an option; Azahar covers all of these.
Cost
Folium is a paid App Store purchase. Azahar is free under the GPL-3.0 license, downloadable from GitHub Releases, Flathub, and the Google Play Store. For users who already own a physical 3DS game library, paying for emulator access on top is an avoidable cost.
Development and Community
Azahar is community-developed with 8,679 GitHub stars, 834 forks, and a public roadmap via GitHub milestones. It has a public compatibility list contributed to by the community. Folium is a commercial product with an App Store release model.
When Folium Fits
Folium is the right pick for iPhone or iPad users who want 3DS emulation installed directly from the App Store without configuring RetroArch. It offers a native iOS experience with no additional setup.
Verdict
For Windows, macOS, Linux, or Android users, Azahar is the clear pick: free, open-source, and actively maintained. iOS users can use Azahar via RetroArch at no cost, or use Folium for a simpler App Store install. If you are playing on any platform other than iPhone or iPad, Azahar is the better-supported, more broadly available option.