sometimes you want an earlier version of itunes that is less bloated or if you are hacking your iphone then you want an earlier version that doesn't stop your jailbreak, etc.
if it were me, i would just take the dive and download itunes from a 3rd party because i like to experiment and customize software to suit my purposes. i also have time machine backups though, don't keep sensitive information on my computer, and am prepared to start from scratch if things don't turn out well
it is up to you to hedge your bets when determining whether to trust 3rd parties