This I find to be the only downside of feeding live, the prey will urinate, possibly defecate before eaten. Though i'm fairly certain it has no ill effects towards the snake as long as regular maintenance is in order I find it quite gross if the prey does happen to defecate or urinate on the snake.
On that note I probably will feed live until I start breeding my own rats and have the surplus to mess around with switching over to F/T. I've tried F/T and personally feel the route of live is more efficient in terms of convenience. Reason being thawing out rats is just not my thing it's gross, I much prefer watching the kill.
One other point I might make is that when it comes to any kind of food, what do we as humans prefer? Only the freshest am I correct? I'm no chef but I could tell you for a fact I could tell when my meat has been frozen or not, I much prefer the latter. So for the sake of giving your snake a better meal to enjoy why not go live?
Then again they don't really chew their food...
But that's still how I look at it.
Once I start breeding I would probably freeze my own rats just because I'll likely be producing a surplus of them.