Having the same program installed in multiple places is not directly a problem, but odds are good at some point the multiple locations will cause problems. For example, if you have the true executable in /usr/local/bin, and have it symlinked to /usr/sbin, that's no problem. If you use yum to install rsync, I think it should live in /usr/bin/rsync. That at least is where Debian places it by default. I avoid rpm distros, so they may place it elsewhere. In any case, what will become an issue is if you just type rsync at the CLI, which rsync are you getting?
if you do
you'll get a list of all the places your user looks for executable programs, and it looks in the order it prints. For example, here's mine:
jim@jimsworktop:~/installs$ echo $PATH
So my machine will first check /usr/local/bin for rsync, then /usr/bin, then /bin etc. If you have the same order, and have rsync in /usr/local/bin, then there is never any need to let yum install rsync, as it will never use it. Once it hits your rsync in /usr/local/bin, it will use that, and stop looking. You can use the full path, ie /usr/bin/rsync if you want that version.
Generally, mixing executables is more trouble than it is worth. I'd stick to the one you have, then uninstall it if you let yum install another.
That being said, I run multiple versions of the game wesnoth on my laptop. I compile the latest version daily, and it lives in /usr/local/bin, so if I type wesnoth, I get the latest and greatest. If I find a problem with that, then I call /usr/games/wesnoth, and get the version installed and kept up to date (not ahead of date) by Debian. It comes down to being specific.