Accessibility of major American English dictionaries

Hi, all, I know that many English dictionaries on the App store are accessible or at least usable (I have two of them installed on my iPhone), but I want to know if the two major American Dictionaries are accessible enough to justify the $24+ price. One is the New Oxford American Dictionary http://itunes.apple.com/us/app/new-oxford-american-dictionary/id298896076?mt=8 and the other is the 5th Edition of the American Heritage Dictionary http://itunes.apple.com/us/app/american-heritage-dictionary/id475661641?mt=8 Personally speaking, I prefer the latter as I've been using its 4th Edition on Windows for some time, but think Oxford's offering is better -- it's smaller (70+MB vs 500+MB), can be used on all iDevices one owns, and, according to many reviews, is crash-free unlike the Heritage offering. Do you know if either of these are accessible enough?