Answer:
LCDs are liquid crystal displays. They are soft and squishy, or can be. Some come with coverings that prevent you from being able to push into the liquid (the squishy).
Plasma is created when the internal gasses (usually neon and xeon) have an electrical current passed through them and become excited. You do no ever touch the Plasma that is created. Those gasses, and thus the Plasma, is always sandwiched in between glass, always.
While most Plasma HDTVs do have a minor protective coating on them, this is mainly meant to help against dirt and some minor oils or such. And often as an anti-reflective coating. It is not designed to protect against cat claws (or other sharp edged things). You definitely do not want your cat pawing at the screen and possibly leaving scratches on it.
And yes, if your cat knocks over the TV, that's a potential for damaging it. But likely about the same as an LCD HDTV. Both would run the same risk of having the screen crack/break if knocked off a TV stand by a cat.
I think your best bet is to wall mount the TV. Find a flat wall where the cat can't access (so nothing near by for the cat to get onto first before attempting to reach the TV) and then put a wall mount on there. Or get a TV stand that has a wall-mount like attachment on it. This way, even if the cat does try to jump on the TV itself, it will be quite difficult to knock it over, as it will be secured, not simply just resting on the top shelf of the stand.
And your cat may well be attracted to the TV. While much better now than in the past, Plasmas still do run a bit warmer than LCDs. So if your cat likes heat or warm object or such, it might be attracted to the TV. I know a friend's cat loves the top of his security monitor at work because of the heat (though not a Plasma, kind of the same idea).
You could also talk to home theatre professionals. Either the store where you bought it, or look for speciality home theatre installation companies in your area. You can't be the first people ever to have bought a Plasma TV while owning cats. So I'm sure they might have suggestions as well.

{ 2 comments… read them below or add one }
yes basically it would just put scratches all over the screen
yes