That's a basic question you can quickly find the answer to by Googling rather than posting and waiting for someone like me to respond
Bitrate is a measure of how much detail is contained in a clip. 17Mbps will give you a smaller file size which will let you fit more/longer content onto a BD. 24Mbps will give you higher quality (clearer details) but at the expense of having less room available.
Unless you're struggling to fit your creation onto a disc, go with 24Mbps.