Coalstack vs Pterodactyl

The short version

These two aren't competing for the same job. Pterodactyl is infrastructure: an open-source panel that runs each game server in its own Docker container, across as many machines as you want, for as many users as you want. It is what a lot of small hosting companies are running behind their own branding.

Coalstack is a desktop application for running your own server on your own machine. There is no panel to host, no container runtime, and no tenants - you open an app on the computer the server runs on, and it is managing Minecraft a minute later.

Where Pterodactyl wins

• It scales past one machine. Multiple nodes, hundreds of servers, and a user system built for giving each customer their own login. Coalstack has no equivalent and isn't trying to.
• Docker isolation. Enforced CPU, memory, and disk limits per server, so one server misbehaving can't drag the others down.
• It is free and open source, with no tiers and nothing held back.
• It isn't Minecraft-specific. Eggs exist for dozens of games, so one panel covers a box that runs more than Minecraft.

Where Coalstack wins

• There is no stack to stand up. Pterodactyl expects Linux, Docker, a web server, a database, an SSL certificate, and the Wings daemon configured on every node. Coalstack is an installer you run on the Windows machine you already own - the difference between an afternoon and a coffee break.
• It knows it is managing Minecraft. Loader and version detection, a Modrinth mod installer and an Auto Debugger that reads a crash log and names the mod that broke it - free, with mod compatibility checks on Coalstack Plus. A general-purpose panel hands you a console and wishes you luck; see the error code reference for the kind of thing it catches. The modpack installer comes in on Coalstack Plus.
• Nothing on your machine listens for strangers. Conduit's remote access works by the app polling coalstack.net outbound, so no panel port is opened on your router or PC for someone to find - the trade being that the relay runs through coalstack.net rather than a box you own. A self-hosted panel is the reverse bargain.
• Your existing hardware is enough. A Windows gaming PC with spare RAM is a good Minecraft server, and doesn't need reinstalling as Linux first.

Which should you use?

Coalstack if the server is for you and the people you play with, it runs on a Windows machine you can reach, and you would rather spend the evening playing than configuring a reverse proxy.

Pterodactyl if you are hosting for people who aren't you - selling servers, or running a community across more than one machine - and you are already comfortable administering Linux. That's a different job, and it is built for it.