Once you start getting to 60" & larger LCDs (even the older ccfl backlit ones) start losing out to plasma's price wise. Between the two you linked, the plasma is older tech. The LCD you linked is a newer LED backlit LCD.
As for is it worth the price over a plasma, it's too subjective for anyone but you to decide IMO. You need to view each and decide for yourself. Keep in mind though that places like Best Buy aren't always the best because you're viewing in a brightly lit (with fluorescent lighting no less) open area and usually the settings are always set on torch mode.
Generally speaking LCD's are better suited to bright rooms (lots of windows, lots of lighting on when viewing) and plasma's are better suited to darker "theater" type viewing. Glare will be a bigger issue on a plasma, and viewing angles will be a bigger issue on an LCD. Other than that, it's pretty much subjective. Plasma's used to be the king of blacks, and probably still are, but the LED LCD's really closed that gap.
If you have any electronics places locally that have a darker/non-fluorescent viewing area for their TV's, that would be the best place for comparing them. They're usually more apt to give you the remote and let you play around with various sets as well, at least in my experience. Also, AVS Forums is a huge wealth of info on particular set's once you have an idea of what you want/need.
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