It depends on your use as to a limited slip vs. a full locker. Now, offroad such as getting all the power to both rear wheels at the same time...the locker wins. On the road..you'll like a limited slip better for the manners and seemless operation. A locker on the road....can be down right dangerous in the wrong hands and wrong environment. The new electric ones that you can turn on amd off (can you even get that option in a 2wd?) gives you flexibility. Since your considering a 2wd I'm going to assume offorad to you is some wet grass turning around or some light snow.
A limited slip is what you seek of I am right. If you are more adventurous....and want to learn what a locker does for you...electric will work great too.