Train to Versailles or book a tour bus?

Not difficult to get there from Paris, although there is construction going on the RER C line through central Paris and I'm not up to date on that. Any way if you can get to Javel on the No 10 Metro line, take a train to Versailles Chateau-Rive Gauche. They are frequent and it is about a 10 minute walk from there. Follow the crowd.

Edit: Checking the RATP site, I don't see any construction issues from next Tuesday onward, so any of the RER C stations along the river will get you there, like Gare d'Austerlitz, St Michel-Notre Dame, Invalides, Champs de Mars. Just plug in your starting point and time into the RATP route planner and it will get you there.
https://www.ratp.fr/en/

Taking the train was super easy. I would do that and then you can take all the time you want.

If you take the train, you can make an effort to arrive earlier than the bus tours which should save time in line and give you more time to explore.

I'd prefer going on my own schedule to see the palace, gardens, trianons and Marie Antionette's "farm" at my own pace and/or stopping for a lunch to the bus tour approach.

Take the train and be on your own schedule. Be aware - when you exit the train station at Versaille there will be several tour companies / tour leaders shouting instructions to newbie travelers who think these leaders are actually in charge of taking you to Versaille. They are not. They're just trying to sign you up for their tour companies. Walk past them and onto the palace.

It is very easy to take the train and see Versailles on your own. Its an easy walk from the train station to the palace. If you want to tour the palace as well as see the grounds, you're going to want more time than what the tour buses allow, in my opinion. If you get there very early, you could tour the palace first. Otherwise, go directly to the grounds as they are less busy and more relaxing. Don't forget the Petit Trianon. Its so pretty. Then after lunch, tour the palace. There is a lovely little restaurant near the lake called La Flotille, which I highly recommend. Enjoy your day.

Train was so easy. You don't want to be herded through Versailles on a tour.

I have a question if I may add to the OPs question... We are leaving for Paris next Monday. We plan to take the RER C line from St Michel-Notre Dame to Versailles next Thursday and spending the day there. Leaving early hopefully our line won't be too long. We plan on buying a five day Paris Museum Pass when we get to Paris and I downloaded the audio guide on our phones. Am I correct that the Kings Apartments are only seen on a private tour?

According to the Versailles website - These spaces are not open for unaccompanied visits, but can be visited during a guided tour most days at 10am, which is an additional 7 euros.

Thank you for confirming. If we do that tour then the main Palace will be quite crowded when we get there. I think we'll skip the apartments.

@ highlanderct: Be prepared for a long wait in the security line if you do not have tickets to the Kings Apartment Tour.

When I went to Versailles, I took the RER-C around 07:10 & was standing in line at the center gate by 08:15. I even stopped by a Boulangerie & picked up some pastries & OJ in route. I was number 3 or 5 in line. By 09:00 there were about 100 or so folks behind me. Once I went through security I followed the signs to the Hall of Mirrors. When I arrived there was only myself, a lady that followed me and two security guards. We took pictures of the empty room & of each other. Then I headed back to the entrance & began my leisurely stroll through the Chateau.

Enjoy your trip.

We did this on our own and had a marvelous time. I think brushtim has a great point - do allow yourselves plenty of time to get to Versailles. I underestimated how long it would take us and we missed our prepaid morning King's Apartment Tour. We were luckily able to get tickets for an afternoon timeslot and went then instead. It was an absolute highlight and I definitely recommend it. I also highly recommend going out to the Petit Trianon and the Hamlet. Those were lovely as well. I would consider renting bicycles or getting tickets for the little train that runs around because it's a really long day of walking if you explore the gardens as well.

This is fabulous information! Thank you everyone for the tips and tricks. Looking forward to our Versailles visit!

The train is easy and the town is a delight - you can see Versailles and then wander the town and enjoy a meal - hopefully you can be there on market day (Tuesday, Friday and Sunday) from 7:00 am to 2:00 pm where you can almost buy anything under the sun