Here's how the two expressions differ:
* "Life throws you curveballs": This implies that life often presents unexpected and difficult situations.
* "May life throw you a pleasant curve": This wishes for those unexpected situations to be positive and beneficial.
The phrase suggests that even when life throws a curve, it could be a positive one. It's a way of hoping for good luck, even in the face of change.
Essentially, it's a humorous way of wishing someone a happy surprise.