it depends on your setup. FOr example, the ebb and grow is made for growing medium to large size plants, where the ebb and flow you can do either, but its good for shorter plants in more abundance, because it sits off the grouidn higher than the buckets, so if your in a closet you couldnt alllow the plants to get that tall. So, figure out your light source, say its a 1000 wats, plan on having it 24 inches above the plants, and consier your height.
Ebb and grow, DWC, aqua farms, larger plants
ebb and flow, aeroponics, for smaller plants in higher numbers.
Yes, flooding is a risk, you should get a pond liner or something for the bottom.
My ebb and grow has flooded more than once and if i wasnt in a grow tent i would have been in big trouble.
If your starting out, consider soil, cheaper and easier, and it will allow you to learn the process of growing