Duplicators work fine. BUT... they essentially scrape the wood, not cut it. No razor sharp cuts when using a wood lathe duplicator. The tear out from these things can be just gawdawful since you are dragging that bit along the profile template.
Making four parts that are exactly the same isn't as easy as connecting dots for me or the others in my club. In fact, one of our challenges was to make fancy, profiled, candle sticks as close to each other in dimension as we could. Two wasn't bad. No one got to four.
But on table legs, that would be different. It is plain spindle turning, and you could put witness marks and depth cuts as needed. It IS similar to connecting the dots in that respect. But the good news is this: If you are off a little, who will know? On our candlesticks we set all of them next to each other and got out calipers to check. YOUR legs will be on four different side of a table.
And if you cut them with a normal gouge, you cut way down (maybe eliminate) tearout and cut down on your sanding. Plus, you're not in for a few hundred dollars for a good duplicating attachment. And it is more fun.
Robert