You’re asking a personal preference question. There are pros and cons to taking a tour or doing it on one’s own. Our preference is to visit on our own. We see what we want for as long as we want. When we’re ready to move on, we move on and are not dependent on when a guide’s talk end. Most of what a guide says, I’ll never remember anyway. When taking an organized tour, if a meal is included, you go to where the tour takes you, not necessary a place you’d choose. If you decide on an organized tour, it should get the tickets for you.
I will add that we generally have a rental car and not dependent on an organized tour or public transportation to get us to and from. If going the independent route, the time of year you’re going will help determine if you should get tickets beforehand. Our last visit there was October 2011 and we just walked right up to the ticket window, no line. Just remember that most tickets bought beforehand are non-refundable so if your plans change, you’re out that money.