If you're using a 4S or iPad 3, and you have your SHSHs for 5.1.1 backed up, I would suggest staying on 5.1.1 solely because of the ability to re-restore to 5.1.1. Same for iPad 2 if you don't have SHSHs for any 4.x revision. If you're using an iPhone 4, 3GS, or iPod Touch 4G, you should just update.
iOS 6 closed a vulnerability that allows devices to be restore without verifying with Apple first. As it stands, if you are on 6.1 and your device is not liable to the limera1n exploit (patched with the release of the iPad 2 and every succeeding device), then if you ever have to restore, you will be forced to restore whatever iOS Apple is signing. Right now, you'll be fine, because Apple is still signing 6.1, but once they've stopped, which won't be long, you will be stuck with a device that you cannot restore without losing your ability to jailbreak.
I am keeping my 4S on 5.1.1 for this very reason. Well, that and the fact that iOS 6 has nothing of worth to offer over iOS 5. On top of that, it adds virtually nothing that cannot be done on iOS 5 with a jailbreak tweak.