In my experience, programmers are often very fuzzy on all of the types involved in such libraries. I don't even mean "strong typing", but just the operations that they can perform with the various chunks of that expression. This is often complicated by the fact that the library itself often has bizarre limitations that have more to do with its internal implementation and limitations than with SQL. It's rare for me to see anyone use a library like that with fluency. Which seems to me to be a valid way of saying that, yes, in practice, it does seem to be harder to understand the first version in Ruby than you might initially think. Using it isn't particularly harder, but understanding it is.

Also note this is an observation of mine, not a logical argument, so trying to logically argue about why it shouldn't be harder would be arguing a point I'm not making. As much as I don't like people bashing strings together programmatically to generate SQL queries due to the ease of screwing it up, I observe that a lot more programmers are capable of this (even if they screw up the security) than seem to understand how to use things like ActiveRecord equally fluently. YMMV.