There are many people who have gone for the standard halogens, only to come back and post a thread along the lines of "How much does it cost to retrofit/upgrade my halogens? I wish I had gotten the Xenon upgrade but I didn't because "
If you live in an urban area with a lot of street lighting, then the halogens will suffice. If you drive in a more rural, xenons are a must. Don't worry about blinding others as headlights are required to have an aim or levelling adjustment* and BMWs with the xenons will have the self-levelling mechanism.
*Does not apply to North American vehicles