は vs のほうが : when to use each one

Question

In the Genki Workbook, it is asked to translate the sentence

"My computer is slower than yours."

I did so using the structure AのほうがBより~ and wrote

「私のパソコンのほうがあなたのより遅いです。」

However, in the answer sheet, it was written

「私のパソコンはあなたのより遅いです。」

After doing some research, I've managed to find that both these structures are correct. However, there are some questions to which I didn't found an answer to:

1) Are there contexts where one or the other structure is desirable, or mandatory?

2) In daily use, which is more natural to say?

Answer 1

This is all about how exhaustive-ga works in Japanese. Both sentences are translated as "My PC is slower than yours", but English speakers mainly use emphasis to express the important nuance which is expressed by の方が in Japanese. If you want to read it out loud like this:

My PC is slower than yours.

Then you'll probably want to use the version with の方が. So there must always be a certain context (e.g., someone said to you "My PC is slower than yours, right?" or "Whose PC is slower?").

On the other hand, the version using は is plainly describing some fact out of nowhere.

My PC is slower than yours.

Probably this happens less often in daily use.

Likewise, 彼は英語を話せます is plain "He can speak English", but 彼が英語を話せます is like "He can speak English" or "It's he who can speak English".