Parking: Sintra vs Lisbon for apartment rentals

You do not need a car in either place. Take trains and trams everywhere. Pick up rental car as you leave Lisbon. Stay in Lisbon.

Well, in addition to Lisbon and Sintra we have plans to go to Tomar and Cascais. Plus, we do not want to be dependent on trains schedule.

If it were me, I would stay in Lisbon. It's the capital of Portugal, and a wonderful and very interesting city. And it's very different from the other major European capitals, such as Paris, Rome, London, etc. Lisbon is smaller, and IMO has a different vibe and ambiance than the larger capital cities.

Well off the top of my head, I'd lean towards Sintra if you are set on getting the car at the airport. We stayed in Sintra and then picked up a car on leaving, but I seem to recall that our hotel had parking. At least some of the hotels that I saw are converted older large homes on lovely grounds, but still walking distance to Sintra's sites. I think it would be easier to do that. You an easily train into Lisbon, they run frequently, and it will set you right downtown. I know you mentioned apartments, but I'm not familiar with those in Sintra. One place in Sintra I saw was Casa do Valle, although I didn't stay there.
We have also rented an apartment in Lisbon. I think it very unlikely parking would be included for a good location. We certainly had none, but loved the location of our apartment

If you have a car in either place, you will probably park it for the duration of your stay and pay for the rental and maybe for the parking too. Rush hour traffic in and around Lisbon (am and pm) can be miserable. Sintra is built on hills, so many of the streets are sharply inclined, most in the historic center are very narrow, with sharp, blind curves. There are frequent trains between the two for a day trip. I took Uber from Sintra to Lisbon Oriente Station at the tail end of morning rush hour so missed almost all the traffic. It was €33 incl a tip (this was 3 months ago). I picked up my rental car there and headed out of town. I don't know why you think you have to pick up the car at the airport, but Uber to the airport from Sintra is about the same fare as to the train station.

If I only had 3.5 days for both cities, I would stay in Lisbon and daytrip to Sintra.

If you stay in Lisbon, you really don't need a car even to go to Cascais or Tomar. There are frequent trains that go there, very frequent in Cascais' case. Traffic in Lisbon isn't very good and parking is scarce. Also, for Cascais and Sintra, at 30-40€ an Uber from Lisbon isn't a crazy idea, if you want more flexibility.
Or if you really wanted to, you could rent a car for a day or two, but not for the whole stay.

Thank you everyone for sharing your opinions. That was very helpful.

Hello from Wisconsin,
Oh gosh don't rent the car until you are ready to leave Lisbon/Sintra. No need for it there, and parking it would always take some joy out of where ever you are headed. I have driven all over Europe and I can not understand why my experienced traveler of a cousin rented a car for his time in Lisbon. He should have known better.

Sintra is small. Lisbon has it all. Train to Sintra for a day trip. Trams will take you all over Lisbon.

To get back to the airport to grab a car is not that big a deal. Or depending on where you plan to head after Lisbon, find a rental there. If you are headed to Obidos or Evora, train/bus it there, stay how ever long you planned to stay and then get your car.

We loved Portugal. Lisbon in late February was enchanting.

wayne iNWI