Hook and backend are different things, and both hard to measure or compare.
Hook will tell you how many boards the ball will be able to cover (with the right drilling, depending on lane condition and bowler's style etc.) from the release up to the pins. But hook or hook potential will not necessarily tell you about the shape of the hook - polished/pearl ball will have an edgier reaction (skip/snap), while dull balls make a rather smoothe curve, reacting earlier. Dull balls will hook more, polished less with a later and more "violent" reaction.
Backend is the ability to convert the ball's revolutions in to a forward move in the final 3rd of the lane, after the ball reached its breakpoint and revolution axis and the ball's path point into the same direction: the pocket. This is physics. The "more" backend a ball has, the better it will be able to convert revs and exploit the energy the player gave it upon release in the pins. I am no technician, but as far as I can tell from observation, balls with a strong backend will be rather low RG balls which save rev energy longer/better than low RG balls.
You can see this effect very well on balls with a balance hole: when it reches the breakpoint, the hole has gone into its final axis, the ball turns towards the pocket and it seems to gain speed - this is the backend reaction.
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DizzyFugu --- Reporting from Germany
"All that we see or seem, is but a dream within a dream..." - Edgar Allen Poe