keep in mind that normally they list dynamic contrast ratios. also keep in mind typically whether this is grey to grey, black to white, etc are not listed. also keep in mind that this number can vary from firm to firm testing the same tv.
generally speaking plasma televisions have much better contrast ratios then lcd (led tvs are still lcd) however, plasma televisions have their own set of issues.
go see the tvs in person and make the judgement with your own eyes. if the contrast looks good to you then go for something in that range. remember, contrast ratios are not the only important thing to consider.