I was anxiously waiting to hear replies to your post contrasting Coimbra to Aveiro. As one does, I second guess my decision this January to choose Aviero over Coimbra. Without experiencing Coimbra personally, I can only tell you what I loved about and why I chose Aveiro.
I wanted a slightly off the beaten bath, colorful, more local kind of place to cool my jets for a couple days. A place I could kick back, enjoy losing myself wandering the canals and streets, observing the pace of Portugal without a tour guide leading a group anywhere in sight. No real must see church or museum per se. A kind of town you might want to day dream about retiring to. I found that in Aviero.
Aviero has beautiful Art Nouveau/Deco buildings and homes lining the canals filled with colorful “Moliciero” boats plying the waters. Each boat is painted with bawdy scenes and sayings. I blushed at many of the translations. The fishmongers at the morning fish market were as inquisitive of me as I them. Traveling solo as a woman in the middle of January, I stood out as the only tourist there. Along the main canal is excellent shopping mall (OMG am I really saying that) that was fun to people watch. It had many great restaurants upstairs that were low stress, you see what they offer before you order places which can be kind of nice after eating at sit down menu type places. There’s a university there to and the town has that youthful vibe. I spent two days/ ights there which was perfect to me. I didn’t venture out to the salt beds or the beach as it was cool in January. Would I go back? You bet. It got me off the tourist juggernaut for a couple days and gave me a glimpse of real Portugal. I’m returning to Portugal in January with a friend this time. Again I’ll struggle wondering if Aviero is a better choice than Coimbra when we break up the Lisbon-Porto traverse. Or will I go with the herd to Coimbra because I have my friend along? I don’t know. This time I would like to day trip to Luso and the natural hot springs at Termas de Luso for a spa day from either Aviero or Coimbra. Again, another off the beaten track town.
Aviero has their Féria de Marca celebration from 3/25 to 4/25 going on and should have Easter celebrations too. Parking and traffic is mellow in Aviero compared to other cities in Portugal. I hope this helps. Whichever you decide, I hope you have a fabulous trip.