I have never used an aftermarket shifter assembly before, and would like to know what are the reasons you would purchase one, other than looking nice. Other than the lockout lever and the ball on top, what are the advantages of having one of these?

(asking before I buy)

The B&M Pro Stick is a positive detent shifter, which means you can pop the next gear and it will stop. No missed shifts. Also the Pro Stick has swapable gate plates which means you won,t have to buy another shifter to go from 3 speed to a 4 speed auto or forward manual to reverse manual, you just change out the gate plate. Gate plates run about 15 bucks each.
I love the feel of a positive detent shifter, I just never liked the rachet type.
Be ready to get creative as far as mounting goes. Its not a bolt in and go deal.

my B&M megashifter was a simple bolt in into my 84 firebird, oh i almost forgot though, i got it specially designed for the third gen camaros and firebirds, had to custom fab the console plate to make it work, but ratchet is the same thing, with punching it forward and it can in no way skip a shift. i like it because with a stall it certainly allows you to easily control gears and rpms without risking the motor over revving because you downshifted too far.

but a ratchet shifter is like a ratchet, 3 locations 1)1st gear, 2nd gear, 3rd gear, neutral, after neutral there is a lockout, and then the next position is reverse and then park, in forward gears you literally ratchet them up or down one at a time. And it honestly is pretty cool to be racing and literally smack the shifter with complete confidence you'll only go up one gear at a time