It depends on what you need it for. The KFire doesn't come with Bluetooth, GPS, 3G, camera, or a built in microphone. So if you really depend on those features then I would get the Galaxy Tab. The KFire is still a great device though. You can read books, watch movies from Amazon Prime, get apps from Android Market, and much more.
Performance-wise the KFire's processing speed is 1Ghz, the same as the GTab but the Kindle Fire has 512mb of RAM while the Galaxy Tab has 1GB. Don't worry about the performance of the Kindle Fire because 512mb of RAM is more than enough. Even the Galaxy Tab only makes 512mb of its RAM usable anyway. The overall performance of the Kindle Fire and the Galaxy Tab are the same though.
Hope this helps!
Sent from my Kindle Fire using xda premium