Nexus is better then both of them for most bots (some on RSBuddy are MUCH better), but if you have to pick between Powerbot and RSBuddy, pick RSBuddy because of the fact that Jagex knows when your logging in from Powerbot, thanks to the person who posted that.
I think you do not load the bot for a while... Yesterday happened an update right before it I loaded the client and my bot was running. They set an autoupdater or something like that and it will download the rs client and update the bot. But yes, some bots then need to be updated to fix any issues but that's not a problem with the bot itself and just with the script.