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

Yes

The word "prefiro" is identical in meaning, spelling, and grammatical function in both Brazilian and European Portuguese. The only difference is phonetic. In Brazilian Portuguese, the vowels are generally more open and clearly articulated. In European Portuguese, unstressed vowels (such as the "e" in "prefiro") are often reduced or "swallowed," making them sound much shorter or more closed to the listener.

Brazilian Portuguese

1. Eu prefiro tomar suco de laranja. (I prefer to drink orange juice.)
2. Eu prefiro ficar em casa descansando. (I prefer to stay home resting.)
3. Eu prefiro usar esse tênis. (I prefer to use these sneakers.)
4. Eu prefiro ir de trem. (I prefer to go by train.)
5. Eu prefiro não comer isso. (I prefer not to eat this.)

European Portuguese

1. Eu prefiro beber sumo de laranja. (I prefer to drink orange juice.)
2. Eu prefiro ficar em casa a descansar. (I prefer to stay home resting.)
3. Eu prefiro usar esta sapatilha. (I prefer to use these sneakers.)
4. Eu prefiro ir de comboio. (I prefer to go by train.)
5. Eu prefiro não comer isso. (I prefer not to eat this.)