Are you talking about torrents? Or what are you referring to as bit clients.
As far as the program goes, it might slightly affect the downloads as some clients are more effective at gathering the information from a torrent as opposed to others. I've tried many and find the simplest ones the easiest to work with, such as uTorrent which is a standalone and very small client. It also depends on your setting and port connections so if you don't have any of those setup, no matter which client you use, it wont help you much.
If you are talking about something totally different, be more clear about it.