I visited the Dali in St Petersburg FL which I really enjoyed.
I'm revisiting Barcelona for 4 days this October. Is the Figueres museum a very different experience? If so, any recommendations for a particular tour group?
Thanks.

I haven't been to the museum in St. Petersburg, but since no one else has answered your question....

The Dali Museum in Figueres is, IMO, a very different experience from just about anything -- I mean, that's what he did, right? Explore the realm of the different! If you decide to go, no need for a tour -- you can easily get there and back by public transportation and walk through the museum(s) by yourself. (In addition to the main Dalí Theatre–Museum, there's a second small museum with his jewelry next door.) And before you go, make sure you consider the opportunity costs -- 4 days is very little time for Barcelona itself.

Sorry I can't provide a direct comparison.

We have been to both. Multiple times. They are similar. If you like Dali, each is worth a visit. St. Pete has some massive paintings, at least one or two of which are displayed in Spain as replicas. The St. Pete collection might be larger, the result of one person's private collection/obsession. Dali had nothing to do with the St. Pete location or display. In Spain, the eccentric building (an old theater) was in his hometown, next door to the church where he was baptized. The layout was his, and it is now his burial place. You could always spend some time in beautiful Girona as part of a day trip from Barcelona.

On the other side of the coin, Figueres can be crowded since it is a popular shore excursion for the many cruise ships that arrive in Barcelona. St. Pete is less of a magnet for large bus groups.

I haven't been to St. Pete. The Figueres museum is fun but it is fair to say that none of his most famous work is shown there; he sold it all off, particularly in the US. But I learned a lot about his artistic techniques and audacious showmanship in Spain.