The background of the question
The Original Poster's question may seem to be about complicated metalanguage on ELL, this is an important question which is addressed in J.R.'s post. However, as I currently understand the OP's concerns, this is not actually what this question is about. It will probably be most helpful to readers here to explain how the question came to be asked and to illustrate my answer here with reference to that particular issue. So this question arose out of considering what is the most helpful way to present items like "after" and "before" to learners.
This is not merely related to the complexity of the meta-vocabulary, it also relates to the complexity of the grammatical analysis of such items. Now in terms of complexity of both vocabulary and conceptual analysis "modern grammar" wins hands down here and traditional grammar puts in a particularly poor show. In order to explain these items, so-called traditional grammar uses the following parts of speech:
- subordinating conjunction
This can be compared with modern grammar, which uses the following parts of speech:
Yes, that's right, there's only one. Now, it's clear that one category is easier to deal with conceptually than three. There is also only one third of the meta-language needed, so we can immediately dispense with a lot of unnecessary extra vocabulary in the presentation of these particular items.
What actually happens to students
Here is what actually happens when language students learn theses items in a "traditional grammar" framework. As soon as they are presented with the items before and after, they are able to use them and understand them in the following types of sentence:
- I'll meet you after the concert finishes.
- I'll meet you after the concert.
- I'll meet you after.
This is because, unsurprisingly, there are parallel items in most learners languages and, let's face it, if you can understand after in one of these sentences you can understand them in all three. Now, this is what happens next when teachers, higher level students, and those learners who undertake the academic study of English as a language start to do any further study of these items. They are told that after in the first example is a subordinating conjunction, after in the second is a preposition and after in the third is an adverb. Unfortunately, this tends to give the people who can get to grips with this a little frisson of excitement. They have more metalanguage and are now in a clique of people who are able to differentiate between items that seem to everybody else to be exactly the same thing. How enlightened we have become.
We may now want to ask what we have achieved by learning this distinction. It seems that what we now know is that subordinating conjunctions take clauses, prepositions take nouns and adverbs occur on their own. The problem is that no learner is ever confused about whether after or before can occur in these situations or not. Additionally, if you take any type of similar word which can only occur in one or two of these situations, learners are rarely confused about this either.
In our yearning to pass on our secret, kabbalistic understanding of the difference in category of words that look and smell exactly the same, we have assigned them to different parts of speech. This has consequences because different parts of speech have different syntactic and distributional properties, which are quite often taught to learners. So when we assign a word to a particular part of speech, learners should expect that those words share the properties of other words in that class. This means, for example that the word outside should share the properties of adverbs when it is not followed by a noun. So a smart student is going to understand from the fact that outside is an adverb that the following generalisations should hold:
- you can't use them after the verb BE
- you can't use them after a noun to add more information for that noun
- you can modify them using other adverbs like very
- you can't modify them using the specialised adverb straight and right
Unfortunately for our learner, none of this is the case. "Outside" displays none of the distinguishing syntactic properties of adverbs at all. In fact it retains all of the syntactic properties of preposition phrases - properties which are the very opposite of the properties described above. This is demonstrated in the examples below.
Adverbs as complements of BE
- *She was happily (ungrammatical)
- *The elephant was locally. (ungrammatical)
- *The assassin was viciously. (ungrammatical)
- The assassin was outside
Preposition Phrases as complements of BE
- She was behind the sofa.
- She was in the cupboard.
- She was outside the building.
- She was outside.
Also, adverbs can't usually modify noun phrases. Prepositions and preposition phrases can:
Adverbs modifying nouns
- *the beautifully woman (ungrammatical)
- *the woman beautifully (ungrammatical)
- the woman outside
Preposition Phrases modifying nouns
- my friends back at home
- the man in the shop
- the man of the moment
- the man outside the building
- the man outside
In addition, adverbs can usually be modified by the adverb very, prepositions usually cannot:
Adverbs modified by very
- He danced very beautifully.
- She'll be here very soon.
- My baboon ate very loudly.
- *The assassin was very outside. (ungrammatical)
Prepositions modified by very
- She was very in trouble. (ungrammatical)
- He was very back. (ungrammatical)
- My elephant was very behind the door. (ungrammatical)
- He was very outside the building. (ungrammatical)
- He was very outside. (ungrammatical)
Lastly, most prepositions and preposition phrases can be modified by the special adverbs straight and right. Adverbs cannot usually be modified by straight or right:
Adverbs modified by straight or right
- *She lived right locally. (ungrammatical)
- *I'll be there right soon. (ungrammatical)
- *She shouted straight dramatically. (ungrammatical)
- She stood right outside.
Prepositions modified by straight or right
- She went straight into the building.
- My elephant jumped right over the table.
- Walk straight onto the platform.
- She's right back at home.
- He's right outside the door.
- He's right outside.
Now, in terms of modern grammar the teaching of these words is easy. Words like before, after and outside are prepositions regardless of what complement they take. You only have to learn one piece of meta-language: preposition. Furthermore, you can sit back and relax, because these words have the same syntactic properties all the time. Simple. What was that? They take different complements? Yes, different verbs take different types of complement, different nouns take different types of complement, and prepositions take different types of complement too. With "modern grammar" it's very simple and elegant. There is one category and this can tell you an awful lot about the properties of the word; knowledge that is useful for learners. With the traditional story it's complicated, confusing and misleading and students cannot use this information productively. There's also much more metalanguage.
The original Poster's question
So with regard to this particular area, at least, it seems that "modern grammar" is more suitable than traditional grammar for the purposes of:
explaining how English grammar lets you express different kinds of meaning, and the different kinds of meaning it lets you express
explaining why one sentence is grammatical and another is not
explaining why one sentence is hard to understand and another is not (when grammatical differences explain it)
explaining what grammatical role a certain word or phrase is playing in a certain sentence
References: All of this info can be found in A Student's Introduction to English Grammar, Huddleston and Pullum, 2005.