Is the word opinião the same in Brazilian and European Portuguese?

Yes

The word "opinião" is identical in spelling, meaning, and grammatical function in both Brazilian and European Portuguese. The only difference is in pronunciation.

In Brazilian Portuguese, the vowels are generally more open and clearly articulated, and the rhythm is more "syllable-timed." In European Portuguese, vowels are often more closed or "reduced" (often sounding like a faint schwa), and the rhythm is more "stress-timed," which can make the unstressed syllables sound much shorter or nearly swallowed.

Brazilian Portuguese Examples

1. Qual é a sua opinião sobre isso? (What is your opinion on that?)
2. Eu não concordo com essa opinião. (I don't agree with that opinion.)
3. Na minha opinião, ele está certo. (In my opinion, he is right.)
4. Você pode me dar sua opinião sincera? (Can you give me your sincere opinion?)
5. A opinião dele não importa para mim. (His opinion doesn't matter to me.)

European Portuguese Examples

1. Qual é a tua opinião sobre isto? (What is your opinion on this?)
2. Não estou de acordo com essa opinião. (I am not in agreement with that opinion.)
3. Na minha opinião, ele tem razão. (In my opinion, he is right.)
4. Podes dar-me a tua opinião sincera? (Can you give me your sincere opinion?)
5. A opinião dele não me interessa. (His opinion does not interest me.)