When compared to, when it comes to, when

When compared to/with; 

When it comes to

Never use when compared to in your writing when all you really mean is  compared to.

The same applies to when it comes to and  many when + present participle

When refers to time.
 

For example, America has higher unemployment when compared with Germany suggests that unemployment is higher only when you compare it, the nonsensical implication of which is that if you stopped comparing it, maybe it wouldn't be higher. Unless you think that  unemployment exists in a quantum state of uncertainty until you look at it, the phrase is absurd. 

The other  horrible thing about that sentence, which I hope you spotted, is that "compared with" itself is wrong. If you have a comparative adjective, you follow it with "than".

The sentence should therefore read:

America has higher unemployment than Germany.  

Here are some more examples of what not to do:
She does better in her tests when compared with other students  -  But whenever she is not compared with others, she does worse? Just use “…than other students”

When compared with your lunch, mine seems far less appetizing (if I stop comparing, will it therefore become more appetizing? Just write: Compared with your lunch, mine seems far less appetizing or, even better, because simpler: “My  lunch seems far less appetizing than yours.”

This school, when compared with others in the district, has more students from China (Stop comparing and the number of Chinese students  falls?)

 

If you start a sentence with "When talking about/discussing/considering..etc." ask yourself two questions: 

1. Who is doing the considering, discussing thinking etc? 

2. If this person or these people  stop thinking abut the thing, would it still be true or important? If so, just say the true and important thing.

When draws too much attention to the  act of thinking, considering etc at the expense of the thing considered.,