I think it might just be on a personal preference. I went with a base design because I have a heavy carpet in my family room. A Plus would be the little extra weight to hold down a monster like these Sonosubs that everyone is building!!! http://frank18202.tripod.com/sonosub...ion/index.html
I took measurements with and without my baseplate and didn't notice any difference. I chose to keep the baseplate because I like the look and it add's weight and strength to the legs. The legs were already strong enough considering I used 5 but the bass adds just that much more. I also used 5 rubber feet under the base which were screwed to each leg. It's very solid on my carpet and there is no way it's falling over.