You seem to be comparing a well-written, large for-loop (that has complexities dictated by true constraints, rather than programmer skill) with a poorly written

You seem to be comparing a well-written, large for-loop (that has complexities dictated by true constraints, rather than programmer skill) with a poorly written functional chain. This isn't quite fair. The functional style nudges the programmer to think in the smallest semantic steps of transformation, in a way that the for-loop doesn't. Of course the programmer can ignore the nugde and write the same messy for-loop using functional constructs, and a good programmer can equally well write a big for-loop in a very manageable and easy to read style. But for an unexperienced programmer seeking general advice, I feel that recommending the functional style (with an additional urge to "listen" to what the style is trying to get you to do) is a pretty safe bet.