I'd like a balance of both, but one thing I've noticed is the writers inability to separate the two.
How many times has a character become personally involved in a case? How many times have we gotten personal character development because it was a friend or relative that's been victimized? How many times have we seen a characters life get turned upside down because of something that happened at work?
I know Miami is renowned for this, but it's the one show I've seen change (and not for the better). Calleigh and her father. That started off amazingly. He appeared randomly and could be in an episode without being involved in Calleigh's case and even when he was, he had a legitimate reason for being there. But then they changed it. Suddenly, he was a victim, suspect, reason for something that went wrong... suddenly he was no longer a character, but a pawn in Calleigh's 'development'.
That was simply an example, there are more (Catherine's ex-husband for example. And Natalia's for that matter).
I appreciate they have to stick an entire case and character development into a 50 min episode, but it gets annoying when the characters never seem to have a life outside of their work. Think about the break room at your own jobs... we talk about our actual lives, don't we? Why not mention a ball game, or a niece coming over in passing? Just hint at it. We don't need to go home and have dinner with them (though there are occasions I'd like that) but we need something to prove they're real people. How else are we supposed to empathize and connect?