travel between Lisbon and Porto

Are you arriving by plane? If so I think the train is the best option. Oriente station is close to the airport. If the weather is nice you can walk, otherwise it is three stops on the metro.

I didn't rent a car in Portugal, but I understand driving there is easy outside of the cities. I spent most of my time in Lisbon, Coimbra, and Porto, and you don't really need or want a car especially in Lisbon and Porto. It would be helpful if you are planning to drive to small towns or coastal areas. I was able to use a bus or train to get most everywhere I was going.

You can fly into Lisbon, take the subway to Oriente station, and get a train to Porto from there, yes. The fast trains don't go to Sao Bento station, the one in the center of Porto. The fast trains go to Campanha station instead, and you have to change to a local train and ride it one stop to Sao Bento (included in the price of your ticket for the fast train).

We had a rental car, and driving, parking, and setting our own route and schedule were very practical. But we didn’t go straight to Porto, and took several days to wind our way north.

I did exactly what you're asking about last summer: I flew into Lisbon, got my luggage, bought a ticket for the metro and used it to go to the Oriente station. Once at the station, I purchased a ticket on a high-speed train for Porto. This was in mid-July, but I didn't have any problem getting a seat on the train (purchased first class). I had scoped out the train times in advance, so I knew how much time I would have. I didn't purchase a ticket in advance because I didn't know if my flight would get into Lisbon as scheduled. As it turned out, that was a good move because I arrived 6 hours later than expected (original itinerary was cancelled: PIT-BOS-LIS changed to PIT-LHR-LIS).

We rented a car for two weeks and could not have visited many places we enjoyed as they are not near train lines.

We are currently in Portugal. When we arrived Lisbon airport we took the metro to Oriente and then the train to Sintra. Could not have been any easier. I think you will find the trip to Porto as easy

If your objective is to get to Porto. I wouldn’t rent a car. If there are places you want to see after visiting Porto, you could think about renting a car at that point.

thank you everyone for the information

Train is best option travel between lisbon to porto The approximate 326 kilometre train trip from Lisbon to Porto takes 2 hours and 37 minutes. The Lisbon to Porto train service, run by Comboios De Portugal, departs from Lisboa - Oriente and arrives in Vila Nova De Gaia-Devesas. 115 trains typically run each week.

We just did this and it was the most stressful part of our trip. Our plane was late coming into Lisbon, we had to bus into the airport from way out on the tarmac and luggage pickup took forever. We took the Metro red line from the airport - there was a long line to purchase tickets, once we got to Oriente we had missed our train . We had pre-purchased tickets for the train to save money but in the end we had to buy new ones. As someone else suggested wait and buy your train ticket at the station. If you have a long wait for your train you can go across the street to the big mall, we had a nice steak lunch there. Oriente station is very confusing, it's huge, has multi-layers and poor signage. You have to make sure you're going up the right escalator to the correct track . The train ride itself was nice.

Plane. TAP airlines. 45 minutes and cheap if you book in advance. You don’t lose a day traveling

"Plane. TAP airlines. 45 minutes and cheap if you book in advance. You don’t lose a day traveling"

This idea was intriguing, so I took a look at google flights. I'm going from the airport at Lisbon to Porto too. My flight lands in Lisbon at 8:30am and there's a flight from Lisbon to Porto at 10am for just 49$. I'm sure it would be a little more with taxes etc., but it might be less stressful to just stay at the airport rather than tackling trains right away. I wonder though, how does it work if I land in Lisbon from Rome, then get on a plane to Porto. Would I have to go through customs? Is an 1 1/2 hours enough time?

You only go through immigration (not "customs") when you arrive in the Schengen Area from outside of it. If you fly into Italy from say the US or Australia, you have to go though immigration. But once you have done that, flying from Rome to Lisbon does not require going through immigration again. It's like a domestic flight.

You could certainly fly from Lisbon to Porto. If you are late and miss your flight to Porto, then you'll either have to buy a whole new ticket (most likely), buy a new ticket on the next flight...or just take the train. If the flight to Porto is cheap, probably not much to risk by booking it. If you miss it, a fast train to Porto is probably not expensive, even at the last minute, as long as it's not fully booked. Just have the train plan worked out as a backup if you need it.

Given how close Oriente station is from Lisbon airport (2 stops away on the metro if I remember correctly), and how relatively cheap same-day train tickets are, I would personally opt for the train. You will have zero stress about missed connections, and Campanhā station is closer to central Porto than the airport.
If you do choose plane, be mindful of TAP luggage policy. I seem to remember that they are very stingy when it comes to cabin allowance, Lufthansa-style.