Any decent pro on a table that isn't gaffed, meaning 4 inch pockets,etc..., would rob the nine ball ghost 9 out of 10 times. At least. Only a bad breaking day with balls repeatedly clustering up would make it interesting.
I suck, and have killed it 9-4, 9-5 on a good breaking day. On buckets, and breaking well, a high B player should give it a good go. I've heard that good players can find a soft break that just opens the balls, and pretty much run out every time. Sigel ran out 28 times in 28 tries with ball in hand in a tourney, according to Buddy Hall. They'll murder the ghost. I can't even imagine how bad Earl would slaughter the ghost on a table like they used in the old Sands events in Reno. Ball in hand five or six ball, who do you like lol?
10 ball ghost seems to be a whole different animal. I have lost 20 in a row without getting anywhere near the hill on tough breaking tables with two clusters a rack (see paragraph above where I confess I suck, though). Pros on a tight Diamond can lose money gambling the ghost at 10 ball. Less balls made on the break, and more clusters make it much, much harder in my humble opinion.
The weird thing is, I've tried the 12 ball ghost and something about the rack seems to help you make more balls on the break so its almost the same as 10 ball. Two or three balls used to scream in the pockets almost immediately on the big pocketed table I tried it on. I don't remember coming close to beating it, though.