There's no way to know for sure what each agent prefers. The word count goes in your book info line (TITLE is a [genre] complete at XX,XXX words) but where you put it is up to you.
A lot of people think opening with your hook and putting the info at the end is the best way to go, while others think an agent will want to know the genre and word count before they read about the book. There's no sure answer, which I know isn't much help. Go with your gut.
ETA: I've always put it at the end, and I've had plenty of positive responses. But then I've only ever queried publishers, not agents.