Wow, I feel like I need to come in here and defend Lisbon!
As others have said, Porto makes the most sense for
@davebugg given his specific situation.
But I'm a bit surprised this is such a landslide. I live in Lisbon by choice so I have obvious biases, although I do like Porto as well. As usual, I agree with
@peregrina2000 that Lisbon has more to see and do (as the larger of the two cities and capital of Portugal since 1255, this is understandable) and completely agree on the grittiness scale. Porto has a bit of a Marseille/Palermo/Naples feel to it (all of which I love), and while there's still some of that left in Lisbon, the historical neighbourhoods are becoming more and more gentrified.
A very quick and possibly not very well conceived comparison between the two cities (IMO, of course!):
What they both have: beautiful and colorful buildings, hills, azulejos, alleyways that are perfect for wandering, great food and drinks scene, old trams (though better in Lisbon!), interesting churches, old Europe vibe.
What Lisbon has that Porto doesn't: Age of Discovery sites (Belém), a castle, more lookouts/viewpoints, home of fado, more 'national' stuff as the capital (e.g. national tile museum), more architectural/planning diversity (e.g. medieval lanes of Alfama, elegant streets of Chiado, 18th-century post-earthquake grid planning of the Baixa).
What Porto has that Lisbon doesn't: a better river scene (better riverside bars/restaurants, more accessible boat trips etc), more accessible vineyard/wine tourism, a bit more grit.
Here are some of my photos of
Porto and
Lisbon on Flickr for anyone interested.
Anyway Dave, I'm sure you'll love Portugal no matter what!