I've never used XCA but I've heard of it. Does it have an actual "online CA" with an API for signing certificates or is it more of a desktop app that works with local signing certificates - like a graphical version of OpenSSL?
If you ever have a reason to check out the `step` / `step-ca` toolchain I'd love to chat about the differences you see. Message me here or shoot me an email (mike at smallstep).