I always play both, but mostly I prefer the "evil" side.
It brought me great moments in the Liara romance conclusion like: "We're heading into a battle to save the entire galaxy and you want to do this now?"
How can you not pick that.
If you want the best of the best, you have to mix it up.
Saying goodbye to Tali in the fight on Earth? Pick the Renegade dialogue, trust me, it's the better option.
In the flatterer scene with Liara, pick the Renegade dialogue. Telling Liara to talk to her father: pick the Renegade dialogue....
But you have to be careful, it's not always Paragon vs. Renegade. Sometimes it's a positiv or negative response, without consequences.
And of course if you don't want characters like Ashley and Kaidan to romance you in ME3. Renegade dialogue is just the friendship path in that case.
It's very confusing, sometimes.
And sometimes it doesn't make any sense, like in the ME3 romance conclusion. Tell Liara always that you love her, the other option is just.... I don't even have an explenation what Shep is talking about.