The past couple years I have turned many people onto american purple top rutabaga instead of using turnips. There is many reasons why and i'd venture to say 95-98% of the people who have switched will never go back except for extreme late planting scenarios. The rutabaga will produce 1.5 times the amount of leaf mass than the turnips. The bulbs are about 50% larger. They also are sweeter as they are slower growing and as a result will be less likely to become woody. They have better disease resistance and insect resistance because of the waxier leaf surface area compared to the rough surface of traditional turnips/brassicas. Turnips are 60 days until maturity and rutabaga are around 90. Here is some pictures in my educational plot, where one should see right away some huge diffferences. When I take people through the plots, they see how disease and insect pressure vary from species and why not all brassicas are created equal.