The only reason to buy a Panasonic soundbar would be if you use your Panasonic TV’s remote control most of the time (which if you have satellite or cable you probably don’t) because a Panasonic brand soundbar would probably allow itself to be controlled by a Panasonic TV remote right out of the box.
This isn’t a trivial thing. When you hook up a soundbar you disable your TV’s speaker and rely solely on the soundbar for sound, so you don’t want to have to constantly switch between the ‘channel’ remote and the ‘sound’ one! Because of this soundbars usually are programmable to be controlled by another remote, but you want to make sure yours will work. If you’re buying at a store take your main remote (TV, cable or satellite) with you to make sure it can control the soundbar you want to buy. If you’re shopping online read the details carefully to be sure it can.
Other than that, just listen to the sound quality. Very often inexpensive units won’t sound much different from pricey ones.
You can buy any ol’ soundbar, but I’ve heard the Panasonics are pretty good.
When people ask me for advice on these things, I usually recommend not buying a soundbar at all and just buying decent bookshelf speakers, a nice center channel, and a midrange receiver. It is, however, more work.