Driving in Turkey or Bus? Better Month to travel?

I suggest April. The tulips will be in bloom in Istanbul and they are gorgeous! Also in April, the days are longer than in October. I don’t prefer to drive because I like to relax while between destinations.

Because Turkey has so many microclimates- the optimal month will depend on your itinerary. October is actually a pleasant month weather-wise as Istanbul has relatively mild weather ( average highs of 67 and lows of 55 degrees vs April’s 62/47) the Turquoise Coast still has warm water for swimming without the very hot weather the summer months bring.
Buses are far more comfortable in Turkey than the US and link most destinations travelers go to. Because Turkey is such a large country. some bus rides are longer than you might care for. For example. It’s a 12.5-hour bus ride from Goreme in Cappadocia to Istanbul and 4-6 hours from Pamukkale to Bodrum. Trains travel on more limited routes, but there is a train route from Selcuk ( Ephesus) to Denizli for Pamukkale that takes 3.5 hours and costs all of €2! The Turquoise Coast in Anatolia is much easier with a car because, once you leave the larger towns, bus schedules are skeletal while a car makes it possible to visit several attractions in one day.
Turkish highways are excellent, but driving should be done during daylight at least for your first visit.

I traveled by bus (solo) all over Turkey and loved it. It was a unique experience and much easier than driving. Plus you could enjoy the scenery and the people. The buses in Turkey are different than in many other countries - most have a lot of amenities, like movies, reclining seats and attendants that spritz you with scented water. :) And the autogars are like airport terminals, filled with huge sleek buses and many agents for the bus lines.

You also get to see lots of locals. I still remember on one bus route, we made a stop so people could purchase something to eat if they wanted. I was good so I stayed in the bus, but a young woman was sitting in front of my with an adorable baby who I had been "communicating" with. When we stopped, she picked up the baby and held her out to me, asking without words if I would hold her. I took the baby and she went inside. So for the next 10-15 minutes, I had so much fun playing with the baby. :) Seems weird, I know, and it would probably never happen in the US, but it was a wonderful experience and one that I treasure.

For example. It’s a 12.5-hour bus ride from Goreme in Cappadocia to Istanbul.

One easy way to break that up is to stop in Selcuk and visit Ephesus, which is what I did. My bus also stopped in Izmir, and I planned a layover there for almost the whole day so I had a lot of time to explore Izmir.

whats wrong with trains where their routes are suitable?

After hearing and reading that Turkish trains are not pleasant or punctual, I really wanted to take a train ride to see for myself. I did last June and was pleasantly surprised to find the opposite was true. The trains are really comfortable, modern, clean and—in many cases,—cost less than a bus ticket for the same route. The one thing I would recommend is buying your train ticket hours or even a day ahead of your departure if possible, because Turks have to show their state ID card and international travelers have to show their passport to buy a ticket and many had to search for theirs when they reached the ticket window. This caused a delay which you don’t want to experience when your train leaves in 20 minutes and the line is moving slowly. Buses, too, can be delayed a bit as claim tickets are written and handed out to travelers so they can reclaim their luggage stowed underneath the bus. This means the bus might depart a a bit later than the schedule.

There is a fantastic interactive train map at www.Seat61.com under the Turkish train section where you can click your departure and arrival destinations for train schedules.
I wish Turkey had trains going to more destinations. It is clear the decision has been made in recent years to prioritize extending the highway system which has benefited cars, trucks and buses.