1. What are pretzels like?

- They are big and soft.

2. What do pretzels look like?
- They are big and soft.
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Which question is suitable?

The first one is better. We can't tell that a pretzel is soft just be looking at it.

Both work quite well.

What do pretzels look like? <~~That's a more specific question. Your first question is so broad, almost any answer would work.

An answer to the second question would be either of these:

They are twisted into a bow and sprinkled with salt.

They are brown and twisted into a bow-like shape.

And at the Texas State Fair, one can get non-soft, no salt, non-twisted, with bacon.

http://cf.creative-culinary.com/wp-content/uploads/bacon-pretzel-rods-unbaked.jpg

What is that prezel like? An arrow headed toward your coronary arteries.
What does that przel look like? A bacon spear headed for the heart.

Looks yummy! :-)

Well, now, pretzels come in many shapes and sizes, soft and hard, salted and unsalted. Some may be fried, others baked. I've read that pretzels are a healthy alternative to chips. That's not the question here. I agree with Ms. Sue. I said the same thing, but deleted the comment about "soft", not wanting the split hairs and confuse the issue.

Both questions are suitable but they require more information for a comprehensive answer.