I've never been terribly clear on the difference between these two. For instance, right now I'm pretty busy with marking and writing report cards. It's a stressful time for teachers. We whine a lot don't we. I'm inclined to say Les bulletins scolaires s'en viennent instead of just ... viennent. I don't know why. Are they perfectly synonymous or do francophones sense a subtle difference? Vos idées m'intéressent.