Streamlabs OBS is based on OBS Studio at its core and is offered free of charge with its integration with the Streamlabs platform its key differentiator. The company has other pretty nifty apps that you can access with the subscription, including VCam, which adds a virtual green screen or background blur to your webcam, and Express Video Editor, which is a quick and easy way to edit your clips to upload somewhere like YouTube. XSplit is the sort of software you can just set up once and leave it alone. XSplit isn't open-source, so the plugins are limited, but equally, there are a bunch built in to make your life better across all the major streaming platforms. The UI is fairly clean and simple and not at all intimidating, and it supports all the various game capture modes, including for DX12 games, capture cards, microphones, webcams, and so on that you'd hope for. Whether that puts you off only you can decide, but it doesn't change the quality of the product behind it. The most significant difference is that XSplit Broadcaster is a paid product with a premium subscription model.
XSplit is an incredibly close runner-up, as overall, there's very little to call between it and OBS. For help getting started be sure to check out our beginner's guide. There's also a healthy community of plugin developers on hand to make OBS even better, and the community really is one of the standout aspects. Of course, the beauty is that there's an immense level of control over all aspects of your stream. OBS also fully supports the latest NVENC encoders from NVIDIA if you're using an RTX GPU for your stream. All you need are your credentials, to set up some basic output settings, where your game video is coming from, and you're good to go. OBS Studio is incredibly powerful, supporting plugins galore, just about every capture card and webcam setup imaginable as well as being able to broadcast to essentially any service on the web. And if you enjoy using it, which you likely will, you really should toss a donation to the dev team to reward them, and help them continue doing their incredible work. And not just a free trial, it's completely free and open-source.
One of the things that initially draws people to OBS is that it's free.