he's got it kind of right, but kinda wrong at the same time.. indicas do usually form bigger, tighter buds, and sativa's tend to form smaller, whispier buds.. but that is about where it stops.. they do produce two very different kinds of highs though.. indica's usually produce a more body stone or couchlock, and sativa's are usually more of a head high.. more soaring and energetic... strength is kinda a false word, if you know what i mean... it depends on the type of high that you are looking for.. indica's usually are used for medicinal purposes.. like pain relief and sleep deprivation.. some indica's are very strong.. like say herijuana for instance.. very narcotic like.. and a good sativa will make you want to work, very creative... if this makes any kind of sense to you..
hope this helps some.....