I like both games for different reasons.
I think the most important difference are:
re: defensive play
In 9 ball if you want to play a safe you MUST hit the ball that you are trying to keep your opponent from having a shot on when he comes to the table.
In 8 ball you don't have to go near the ball or balls your are trying to keep your opponent from hitting when he comes to the table.
re: offensive play
In 9 ball you must make the smallest ball and achieve leave on the next smallest ball.
In 8 ball you can make any one of you group and get leave on any other one of your group.
re: luck
In 9 ball if you accidently luck in the 9 you win.
In 8 ball if you accidently luck in the 8 you lose.
I think the most important difference are:
re: defensive play
In 9 ball if you want to play a safe you MUST hit the ball that you are trying to keep your opponent from having a shot on when he comes to the table.
In 8 ball you don't have to go near the ball or balls your are trying to keep your opponent from hitting when he comes to the table.
re: offensive play
In 9 ball you must make the smallest ball and achieve leave on the next smallest ball.
In 8 ball you can make any one of you group and get leave on any other one of your group.
re: luck
In 9 ball if you accidently luck in the 9 you win.
In 8 ball if you accidently luck in the 8 you lose.