TOEFL and IELTS are better. TOEFL and IELTS are both language tests, focusing on language ability and practicality. Therefore, vocabulary is generally common vocabulary and some basic academic vocabulary. IELTS and TOEFL have all passed. I feel that IELTS vocabulary is more suitable for daily use, and it is based on CET-4 and CET-6. IELTS has no certain vocabulary restrictions and rules. The TOEFL vocabulary will be a little more academic, about 8000. But actually, I think it's similar. After all, it's just a language test.

GRE is a postgraduate entrance examination in North America, so the vocabulary is quite large. There are 20 thousand-22 thousand. The vocabulary in it is very academic and uncommon. Some words are not used in my life except exams. But it can't be said that GRE includes IELTS TOEFL, because the emphasis is different. But if you can master GRE vocabulary well, TOEFL IELTS should be no problem.