Well, here comes the standard response: They both (plasma or led/lcd) have their advantages and drawbacks, This subject gets argued about a lot here.
I have a 7 year old 42" plasma still going strong, and a couple LCDs, and a 65" LG LED/LCD I got about a year ago. I don't regret getting the LED at all. It doesn't quite compare with current plasmas for black levels or most other respects, but it's "good enough". Newer plasmas are significantly better than mine, but LED/LCDs have improved as well, and my 65" LG looks better than my older LCDs And it's a lot brighter than my plasma with good whites, which may or may not be important to you. I watch a fair amount during daytime and don't want to darken my home theater, although I could. I also usually prefer some bias lighting in the evening and night.
It's going to depend on what matters most to you. The Panasonic plasmas are very well thought-of here, and reasonably priced. Again, since you already have a plasma, you should at least have a look at them. If you want an LED that rivals a plasma for picture quality, have a look at the Sharp Elite or a top-end Sony. If you're not a purist and your budget won't go so far, there are more possibilities.