Is a 4.1 channel soundplate for my tv better than a 2.1 channel soundplate?

the correct term is "soundbar"

you may want to read http://www.ebay.com/gds/THE-SOUND-BAR-CRAZE-HOME-THEATER-OR-NOT-/10000000009624483/g.html

and it really depends. given that all of the audio is coming at you from the front they are not going to be the same as an actual surround sound system however some of them with the advanced processing, delay or multiple speakers can certainly create an effect that is more than just stereo sound and works fairly decent to create a surround-like effect.

the best advice is to listen to them in person or if that is not possible, read reviews on the individual models to see what people thought about the sound quality.