"Are they comparable to Indigos when it comes to smell, defacation , etc."
No, indigos have a faster metabolism and are generally more messy. Black pines are like any other large colubrid when it comes to the poop department.
"Are they born black or with a pattern so how do you know how "solid" black they may turn out?"
They are almost always worn with some pattern...usually more so towards the tail. They get darker as they age. If you want a darker animal as an adult ask the breeder to see photos of the parents or pick a hatchling that is darker than the rest.
"I am not a novice herper but am looking for a robust solid black animal just for a pet. I am also looking in to the Blackmilksnake direction but am undecided. Does anyone have any suggestions."
It really depends what you're looking for. Black milks are awesome and are typically docile lap snakes that are easy to care for. They won't be solid black snakes for the first couple years. Black pines usually have more attitude but also more personality IMO. Both are great snakes but if you're looking for a snake that is like an eastern indigo, I'd save up a few more bucks and get the real deal (assuming it is legal to do so in your state)
Good luck,
You can't go wrong with either choice. I've kept and bred black milks and black pines and they are both a pleasure to work with. You can throw Mexican black kings into the mix for another good choice.
Chris