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

No

The spelling, grammar, and fundamental meaning of "preferia" are identical in both Brazilian and Continental Portuguese. However, there is a difference in typical usage and pronunciation:

• Usage: In Brazilian Portuguese, "preferia" (the imperfect tense) is frequently used as a colloquial substitute for the conditional "preferiria" to express a polite "would prefer." In Continental Portuguese, speakers are much more likely to maintain the distinction, using the conditional "preferiria" for "would prefer" and "preferia" strictly for "used to prefer."
• Pronunciation: The phonetic realization differs; Brazilian Portuguese tends to have more open vowels and less reduction, while Continental Portuguese features more significant vowel reduction and a different rhythmic pattern.

Brazilian Portuguese examples:

1. Eu preferia um suco de laranja. (I would prefer an orange juice.)
2. Ela preferia brincar no parque. (She used to prefer playing in the park.)
3. Nós preferíamos viajar de carro. (We used to prefer traveling by car.)
4. Você preferia que eu ficasse? (Would you prefer that I stayed?)
5. Eles preferiam chocolate amargo. (They used to prefer dark chocolate.)

Continental Portuguese examples:

1. Eu preferiria um sumo de laranja. (I would prefer an orange juice.)
2. Ela preferia brincar no parque. (She used to prefer playing in the park.)
3. Nós preferíamos viajar de carro. (We used to prefer traveling by car.)
4. Preferias que eu ficasse? (Would you prefer that I stayed?)
5. Eles preferiam chocolate preto. (They used to prefer dark chocolate.)