As for which exam is easier, I think it really depend on different person.
For me, GRE is way easier than GMAT.
I have a really good memory and I love to study vocabulary. In GRE, for the vocab part is like either you know it or not. The strategies don't really help. I made it to 90 percentile in verbal. I got a perfect score on GRE math. GRE math is way easier compare to GMAT math.
Although I also made perfect score on GMAT math, but GMAT verbal is a totally different story for me. I am not a logical kind of person. Even though, GMAT verbal part does not have much vocab, but I just don't get that. The highest verbal score I got from varies attempt is 28 on the real test, which is about 40 some percentile only.