my general comment, from one polyhedric in coding (and actually my first question in tackling a general programming/coding problem is "what is the best language for tacking this) is that all major IF parser-based language has is strenghts.
TADS 3 has by far the best support for NPC handling, when I7 has by far the best support for act-based IF and an excellent handling of adaptive prose (said handling even got implemented in TADS3.1.x), and ALAN has the maximum flexibility in parser definition (from verb-noun to a sophisticated one) and together with Hugo, are the easiest to code.
TADS 2 and Inform 6 are very flexible and have a large contribuition library, and are the twin foundation stones of IF programming. IMO, a serious IF coder must know both as their hands.
Lastly, Dialog is the “black horse”, based on goal-orienting general-use language (Prolog), and I think that a goal-oriented language can be be an interesting innovation in IF coding.
of the “legacy” IF language, ZIL/ZILF is, for obvious reasons, by far the major one (now having unquestionably the best set of source code examples…), when advSys and ADL have their foundation in LISP, and strong as object-oriented language, but for me, even with modern editors and syntax-checkers, I can’t suffer more than a pair or three nested same-type parenthesis (I have no issues with mathematical parenthesis nesting {[()]} <— as those) when AGT/Magx trade true programming with ease of use, and remain good for non-sophisticated IF.
Scottfree suffer from the original author lost under bo(u)rne again, if one catch my drift, and indeed I’m still prodding him for info on the remaining issues in decoding his format, but scottkit is an excellent language and sac is “without infamy nor merit”, as we say in Italy. (if scott2zil is modernised, should be possible to even use scottkit as I6 frontend, like I7)
that’s all. sooorry for the wall of text 
but I suppose I have done a worthwile perspective on current parser-based IF language scene.