Turn, Turn, Turn

It's INFINITELY easier to turn heel, because there's a million things you can do to make people boo you for no reason. You can put your feet on the ropes, hit a guy in the junk, punch out the ref, slap some annoying old lady at ringside, spit on the beloved quarterback of the local high school football squad, steal a little kid's t-shirt and use it as a makeshift jockstrap…whatever. Point being, do any of that and the fans will immediately clue in. Might not be effective in the long run, but people will take the hint right away. Babyface turns are trickier, because you generally have to know how to manipulate the crowd into cheering for you, or else have something scripted around you where you save someone from a beatdown, so it's kind of out of your control. So yeah, I vote turning heel as easier.