Is the main difference between these two lines overall quality (high end vs low end)?
I thought I was set on a Sony DCR-HC42 until I read some negative reviews on it. It was getting 3 out of 5 star rating from users on another website. Now I am looking at the Canon line and I wanted to ask the main difference between the Elura and Optura lines. Next, I would like to ask what do all these numbers such as 60, 70, 80, 85 and 90 mean? Is the higher number necessarily the newer and better model?
I am not very technical so appreciate easy answers please! Thanks in advance.
p.s. It is for my son graduating college and I want it to be small enough to fit someone's palm and coat pocket.

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