COMPARED TO and COMPARED WITH

[klater]

Manhattan GMAT 5th editon Chapter9 P152

it says The GMAT deems COMPARED TO and COMPARED WITH as the same. So I don't understand why the sentence "Compared with a horse, however, a zebra is very hard to tame." is right while the other one "When compared to horses, zebras are vicious." is wrong?

is it because of When?

what if I change it to As?

is the construction "As [past participle], [subject]..." correct?
For example, "As discussed, the meeting will be postponed to tomorrow."

[RonPurewal]

The problem is the "when". With "when", you're implying that zebras only get vicious when someone makes that particular comparison.

I.e., let's say I have a friend who looks like a monkey. Understandably, he would be mad if this resemblance were pointed out to him.
When compared to a monkey, my friend gets mad. --> Yep.

You see the problem here.

[RonPurewal]

As discussed, the meeting will be postponed to tomorrow.

This is acceptable usage, but I'm not sure whether I've ever seen it in a gmat problem.

[klater]

The problem is the "when". With "when", you're implying that zebras only get vicious when someone makes that particular comparison.

I.e., let's say I have a friend who looks like a monkey. Understandably, he would be mad if this resemblance were pointed out to him.
When compared to a monkey, my friend gets mad. --> Yep.

You see the problem here.

Thank you for your reply. I understand it now.
But what about "As compared to horses, zebras are vicious."?

[RonPurewal]

Have you actually encountered "as compared..." vs. "compared..." as an issue in a gmat problem? If not, it's a non-issue.

You'll likely see just "compared" rather than "as compared", but there's no reason to worry about it unless there's a reason to worry about it.