Looking for advice on which tour to take in the Palace - Will be there week of May 10th - will booking tickets ahead of time save me much time?
As always thanks in advance for the info

Walk up and buy the 40 room tour with the audio guide. I have done it twice,and never saw that advanced booking would have done any good. In fact, I did not know it was possible.

The "out" buildings are interesting as well. The Gloriette is a fair pull up the hill, but it is worth it for the view.
The U bahn stops very close to the door.
It is a short walk from the station to the actual entrance because the courtyard is large and the building itself is set well back from the street.
Take line U4, direction Hüttelsdorf. It is 6 stops from Karlsplatz, 5 from the West Bahnhof with one change.

We arrived when they opened and took the shorter, 25 room audio tour, which was plenty in my opinion. Bob is right about the Gloriette and the gardens. The carriage house is also interesting.

You can visit SchÖnbrunn without the walk from the U-4 U-bahn stations.
Take U-3 or U-6 to Westbahnhof.
Exit to the street and take Tram ( strassenbahn) # 58.
It will take you directly to the main entrance to Schönbrunn.
Try visiting in the afternoon hours and on a week day. It seems many more tours are there during morning hours.Weekends bring crowds of tourists from nearby countries.

We took the full tour and thought it was worth the extra time. Our guide was entertaining and fun and we saw things that aren't included on the audio tour. (FYI, some people on the audio tour tried to tag along onto the back of our group and were chased away by the guide, so don't try that.)

We were glad that we took the 40 room tour because the rooms that we found to be the most spectacular were those that were not included in the 25 room tour.