'Using a keyboard is better' v 'It's better to use a keyboard': and why IT with the infinitive?
We often use gerund-participle clauses when we want to use a verb as a Subject:
- Smoking is bad for you.
- Using a keyboard is better
In English, we don't like to use infinitival clauses as Subjects, though. Although to do so is grammatical (see what I just did there?), it places a lot of strain on the listener. The following sentence is grammatical, but is arguably rather clunky:
- To use a keyboard is better.
To get round this problem, speakers often use extraposition constructions. We stick a meaningless dummy pronoun, the word it, in the Subject position and move the clause to the end of the sentence, where it appears after the verb phrase:
- It is better to use a keyboard.
In the sentence above, the word it has no meaning. It just fills the Subject position to make the sentence grammatical.
Gerund-participle clauses, however, very rarely occur in extraposition constructions (we need very special circumstances to be able to do so). The word it in the following sentence will not be interpreted as a meaningless dummy pronoun. Rather it will be understood as referring to some previously described experience or situation:
- It's better using a keyboard.
All of these cases are obviously making a comparison to something previously mentioned, which isn't disclosed in the question. I'll describe some situations in which your sentences would be what I would expect to see.
- Using a keyboard is better.
Person 1: "My tablet has a simulated on-screen keyboard, but I find it hard to type because there is no tactile feedback."
Person 2: "Using a keyboard is better."
The keyboard is the subject of the sentence and you're comparing it to the previously mentioned alternative.
- To use a keyboard is better.
This is an awkward construction that I wouldn't expect to see in normal speech. Starting a sentence with "To use a keyboard...", I would expect it to be an instruction: "To use a keyboard, plug the connector into the back of your computer."
This would not seem to be part of a direct comparison to something mentioned just prior, so the "is better" seems like a non sequitur.
- It's better to use a keyboard.
Person 1: "I need to input a lot of text into my computer. I'm thinking of using a microphone and voice-to-text software to do it."
Person 2: "It's better to use a keyboard."
The difference I see between 1 and 3 is a nuance based on use of the infinitive and the subject of the sentence.
"To use a keyboard" refers to it in the abstract, more as a method than a direct action. That is coupled with the subject of the sentence. "It" refers to the task. So sentence 3 describes an alternate way to accomplish the task more than comparing the keyboard to something else.
- It's better using a keyboard.
This is the "optometrist" example, "Is it better this way or that way?"
Person 1: "Do you prefer using the on-screen simulation or an actual keyboard?"
Person 2: "It's better using a keyboard."
This construction reminds me of a 1960s Coca Cola slogan: "Things go better with Coke!" Sentences 1 and 3 focus on the keyboard or the task for which the keyboard is a critical element. Sentence 4 seems to focus more on comparing the experience of performing the task in different ways, with the keyboard as a variable.
Comparing sentences 1 and 4: sentence 1 starts with "Using a keyboard", making the keyboard the subject of the sentence. Sentence 4 starts with "it", making the process or the comparison the subject of the sentence.
Comparing sentences 3 and 4: "using a keyboard" describes the action of using it. "To use a keyboard" refers to it more abstractly as a method. So the difference is somewhat like using either "if" or "when":
It's better (the task can be accomplished more effectively) if you use a keyboard
vs.
It (the experience) is better when using a keyboard.