There are plenty of threads already on this topic...
Anyhow, IMO Windows RT is nigh-useless without jailbreaking. 8.1 helps a little but it's still pretty bad. On the other hand, the RT hacking scene has lost a lot of steam while waiting for an 8.1 jailbreak to come out, and most of the apps that were ported or created specifically for RT are now obsolete versions, abandoned partially complete, or both. They are still useful, but there's limits.
In any case, it really comes down to your use cases. If you need Outlook, use 8.1. If you want to run DOSBox games, use the jailbreak. If you need the latest and greatest Windows Store apps, use 8.1. If you want to try running the x86 dynamic recompilation layer (one of those incomplete-and-abandoned projects, though it works for some normal Windows apps) use the jailbreak. If you want to run the latest version of IE, use 8.1. If you want to use a mostly-functional WebKit-based browser (i.e. not IE), use the jailbreak.
Or you could try contributing to getting the jailbreak working on 8.1, I guess. That would be the best of both worlds, and would probably jump-start development for RT again.