Is a trip to wroclaw or Poznań a worthwhile visit

They are both attractive, but there seems to be nearly universal agreement that Wroclaw should have a higher priority than Poznan. Wroclaw seems to have more to see. Whether it make sense to include either one in your trip depends on where you will be traveling from and how much time you have allotted to that earlier stop and to Prague. For example, I wouldn't give up a fourth or fifth night in Prague to squeeze in Wroclaw unless I expected to make additional trips to Czechia but not to return to Poland.

Wroclaw - Yes
Poznan - No

What would be best things to see in Wroclaw? Is one night enough?

https://community.ricksteves.com/travel-forum/trip-reports/four-cities-in-poland-2019

What would be best things to see in Wroclaw? Is one night enough?

I'd say 2 nights minimum, 3 nights+ if possible. There are a number of things to do in and around Wroclaw, I liked the Old Town Hall and Market Square, Cathedral Island, Centennial Hall, Zoo Wrocław, The Panorama, City Museum of Wrocław, Museum of Archeology, City Arsenal Museum.

We lived in Poznań for a couple of years, and loved it. The Stary Rynek (Old Town Square) is lovely, and I found the cathedral exhilarating. Very stark Gothic. We enjoyed the open markets, and there were some lovely parks. The public transportation was great.

Now, I will say it has been many many years since we were there; perhaps someone who has been there this century has some recommendations for you.

I like them both. Wroclaw is of greater importance for those interested in Pope John Paul II's life.

I've been to both and loved both. I unfortunately didn't get to spend much time in Poznan and the weather during the time I did spend there wasn't the best, but I thought the city was beautiful and it has a lot of street art which I love. I spent 5 nights in Wroclaw and would have to say it edges out over Poznan. Definitely a city worth a visit. I loved the Botanical gardens and the unofficial scavenger hunt of gnomes. All the canals, bridges, and manmade islands create quite a beautiful cityscape. Wroclaw deserves at least two nights though.

I thought Krakow was beautiful, but every time I asked a local what we should see, the answer was almost always, ”Wrocław!”