Using pre-trained word2vec vs re-training a word2vec model
As always, "is A better than B" always depends on what you consider better? Is it accuracy, is it speed etc.

The dumb but correct answer to your question is: "try both and see which one is better".

Performance of techniques is always to some extent dependent on the data. What you need to remember with word vectors, is that they are learned based on a certain context. If the context that was used by Google's model is similar to yours, you might be better off using their model. But if it's different, you might run into some problems.

Just imagine the following case. You have 4 words: King, Man, Queen, Woman. Which pairs of two words would you create? Depending on the context, you could make a case for several


King/Man and Queen/Woman because of gender
Man/Woman and King/Queen because of the use of the word etc.