By plastic base, I assume that you are talking about the sectional track with built in roadbed. Like many things in model railroading, it depends on what you are trying to achieve and your budget and skill level. For a beginner, the sectional track with roadbed gets you going in a short time with minimal effort. It can be used on the floor, on a dining room table or wherever. The flextrack does a better job of realism but requires more work, since you have to use adhesive and/or nails to install it. You also have to provide the roadbed separately. Usually cork or foam, although there is one company still making wood roadbed, I believe. When you get into the nitty gritty of model railroading, you will find that there are several options of rail size, tie spacing and other things that you can do to make your layout realistic. Check some of the beginners books available at hobby shops.