Somewhat the opposite of Lisbon in the Meridien vs Sheraton comparison.
Meridien
Arrived in evening, but that is not a factor in my impression. In short, pass on this hotel. Dark in lobby, in room and hallways. Somewhat helpful staff. Bed was comfortable.
Sheraton
Ok, to start off, I walk in the door, approach the staff for help and .... WOW !
Quite different from Lisbon Sheraton where check-in desk staff say to speak to the concierge, the Porto check-in staff is helpful (technically, before I'm a guest) and only on a couple of questions later in stay was I directed to the concierge -- yet check-in staff had much better recommendations for attractions, restaurants, things to do, transportation, specialty stores, events, very knowledgeable on hotel's facilities. :-:
That was all before a review of the Platinum amenities (same as Lisbon) and going to the room. So, things couldn't top that you think? Absolutely, positively, they were topped ... I was escorted to the room, while features of the hotel were described, and the room was AWE-mazing - corner suite, two plasma screens, huge bathroom, with see through glass (with electronic blinds), a table for four, two couches, all in a softer colours. And, I'm only staying one night? Argghh, I thought, and with very helpful, friendly, knowledgeable reception staff...and I can't recall exactly what preceeded it, but I was informed the staff could contact the airlines for itinerary changes, alternate travel arrangements, etc... like someone reading my mind... double WOW!!
Later in the day, a printed message was there waiting with the few alternate travel possiblilities researched. :-:
Club Lounge, Outdoor bar area, whole lobby were great. Did not try the restaurant, but the menu did look interesting.
Next day, more suggestions followed from prior day reception staff, along with an introduction to the manager who indicated a slight problem with an Evora reservation, but that they really wanted to help out. These sent me slightly off the beaten path on discovery of other parts of Porto where I saw fewer tourists. And a newer restaurant about 50/50 locals and tourists.
On third day, was disappointed the reception staff from first day was not present (perhaps a change in shifts or a day off?

). Though I continued with the suggestions from the prior day and at the train station one of the local free newspapers was handed to me and I noticed a wine festival of Aligo and a Galician town in the newspaper, so I made another excursion - when I informed the staff then on duty I would possibly check out they indicated to let them know by 2pm and they even provided a couple of hotel suggestions along the Duruo.
Thoroughly enjoyed the stay and have probably forgot to mention several other things. This is one place I would definitely return to! :-: ^ ^ ^ ^ ^ :-: