A huge difference between Words with Friends and Scrabble is how bingos are treated. In Scrabble/Words with Friends parlance, a bingo is when you can use all seven letters on your rack to make a word on the board. It's not easy, and you're rewarded 50 bonus points for your effort on top of the score.
But wait a minute -- that's only in Scrabble. In Words with Friends, bingos are only worth 35 points. What does that imply? It might mean that in Scrabble, building your rack (and thus holding onto letters) is a more important strategy. In Words with Friends, the benefit of playing medium-sized words (especially those that can get you on a bonus square) becomes way more important than one big word. You put an X on a Triple Letter square, and you've got yourself 28 points right there. It might not be worth it to wait just to get an extra 35 points and possibly miss the bonus.
Of course, this is counteracted by an important factor: No matter what platform you're playing on, you're still trying desperately to impress your opponent with dazzling skill. In that mindset, a bingo is always welcome.