I got rapier first but now I have all chaotics and I like Longsword the best but if you're only getting one Chaotic and you're going to be using it as your main wep for slayer, pvp etc, then I'd recommend rapier but it's all personal opinions and you should pick the one which applies to you so give the thread a read which Libbie linked you and make some decisions from there. There's also some good comparison videos on YouTube made by a video maker called 'FangzorRS' I think that's his name and there's many others, too.