Justified or left-aligned?

In the late 1980, when I was in thrall to the possibilities of the nascent personal computer, and in particular of the word processor, one of the things that excited me the most was the prospect of "justifying" my text - just like in books! I remember how surprised I was to learn from the lips of our resident IT expert that justified text was in fact more tiring to the eye than the usual left-aligned text, as used in handwriting and on a traditional typewriter.My IT friend was absolutely right. My justified writings on my state-of-the-art Amstrad PCW looked unappetising in the extreme, especially when printed out. Was this because my computer's puny brain was unequal to the task of distributing the spaces appropriately between the words and because it did not take on board the rules of hyphenation? I had no idea how complex the latter were/are until I was once required to check a translation for word breaks. it is a whole new world. Anyway, I notice that just about all text on the web is left-aligned whereas in most books it is justified.

In the late 1980, when I was in thrall to the possibilities of the nascent personal computer, and in particular of the word processor, one of the things that excited me the most was the prospect of "justifying" my text - just like in books! I remember how surprised I was to learn from the lips of our resident IT expert that justified text was in fact more tiring to the eye than the usual left-aligned text, as used in handwriting and on a traditional typewriter. My IT friend was absolutely right. My justified writings on my state-of-the-art Amstrad PCW looked unappetising in the extreme, especially when printed out. Was this because my computer's puny brain was unequal to the task of distributing the spaces appropriately between the words and because it did not take on board the rules of hyphenation? I had no idea how complex the latter were/are until I was once required to check a translation for word breaks. it is a whole new world. Anyway, I notice that just about all text on the web is left-aligned whereas in most books it is justified.

Which of these two blocks of text is more tiring on the eye? To make the comparison easier, I should really place them side by side instead of of one on top of the other, but I don't know how to to do that, at least not in Blogger.