Reason is a great piece of software. You can load REX files into it's Dr. Rex player and you'll be good to go. Alternatively, you can also load loops into it's NN-XT sampler and fool around with the parameters to mangle up your loop. Reason's biggest limitation? It's doesn't record a wav track so you can't add vocals to the mix. This is where Fruity Loops goes one over Reason.
Battery is a Native Instruments drum/percussion sample playback plugin. It gives you very realistic drum samples that you can play using midi - the MPD allows you to play the samples live. Battery is not a loop playback synth although, in theory, you can load a loop into one of the "pads" and trigger them with midi. The purpose of Battery is to give you excellent samples of drums far above what you usually get from a cheap sound module, free soundfont, or even the included TTS-1 synth in Sonar, e.g.
If loops and pattern based sequencing are what you're after, either FL Studio or Ableton Live is best for you, with Reason a close second since it doesn't record audio.
