A colleague recently brought my attention to an article by Mark Rippetoe entitled "Crossfit and Functional Training: The Fundamental Problems" which I first thought was simply another Crossfit bashing article (it's not) but contained several good points regarding the benefits of strength training and the term "functional training."
I stopped using the term "functional training" a long time ago unless if I'm trying to help someone literally get out of bed, out of a chair, off the floor, etc. I feel the most effective exercises tend to be the simple ones and higher degrees of complexity rarely translate into improved functional movement (unless as Rippetoe mentioned the goal is to improve performance in that specific particular complex task which is rarely the case). Oftentimes I think the term "functional training" is incorrectly applied to exercises involving complex compound movements with unnecessary elements of instability or coordination thrown in under the premise that proprioception or core stability is being challenged. And they very well may be, but exercise prescription, variation and progression should always be determined with the desired goal in mind. To what degree does task complexity help the subject progress towards the goal? Surely there is a ceiling effect or diminishing returns after a certain degree.
The common theme in most of Rippetoe's work appears to be the stance that strength trumps everything, which makes sense given that he is a strength coach. While I do believe strength is one of the most important elements of training and rehab, I think emphasis must also be placed on performing movements efficiently and with the most optimal strategy. And all this must occur in the context of the goal in mind, whether it be to run following an ACL reconstruction surgery or a powerlifting competition.
I forget if it was Mike Boyle or Dan John but one of those guys also wrote a similar article on why strengthening trumps conditioning in the context of sports performance, which I'll post later if I happen to find it.
I think metabolic conditioning is fun and has it's benefits, but strengthening with gradual progressive overload over time when done safely and correctly can elicit longer-lasting and beneficial training adaptations. Doesn't mean metcon/HIIT and true strengthening have to be mutually exclusive but if you do a lot of the former, you better make sure you're incorporating the latter on a regular basis.