When planning a day trip to Toledo, I would stay with the option of reaching Toledo by train even though the bus ride costs much lesser. The AVANT train from Atocha gets you to Toledo in 30 minutes, and costs about 25 euros for a round trip.
On the other hand, bus journey is long and boring. The bus ride can take as less as 50 minutes or as long as 2 hours, depending on the bus service you take and the traffic on the day you are traveling to Toledo. So, for a day trip I certainly don’t recommend the bus even if it is cheaper. Also, unlike the train ride that passes through scenic countryside and small towns, the bus journey to Toledo is very drab and uninteresting, passing through the city and outskirts which are full of people, buildings, and traffic.
However, if you are close to Plaza Eliptica bus station in Madrid, the 11 euro round trip by bus could be even more tempting. This way you will arrive close to Plaza Zocodover. From here a short bus or escalator ride will get you to the highest point - Alcazar - of Toledo, where you can start your visit and make your way downhill. This is also convenient because the mini train for visitors also picks passengers at Zocodover.