lucy24 - 10:01 pm on Feb 24, 2012 (gmt 0)
The first. The second is the "unexpected results" version. And the line should go in your top-level htaccess, because auto-indexing would normally be off by default. (You can turn it on in individual directories.)
Turning specific options off or on has no effect on other options. The default is "All", which means ... "All except MultiViews". (At least it does in Apache 2.2. It may be necessary to add this disclaimer to all statements about Apache everywhere ;))
Any options preceded by a + are added to the options currently in force, and any options preceded by a - are removed from the options currently in force.