How many points should one need to vote down?

Question

On Physics SE, one needs only 15 reputation points to vote up, but 125 points to vote down. Do people here consider this scheme good enough for us too? Should the points needed to vote for both directions up and down be the same? Other suggestions?
 

Answer 1

Arguments for yes, copy SE:

• One may use upvoting as a way to saying "thanks", etc.
• Downvoting needs some more amount of knowledge of the topic.

(I disagree with this opinion, so consider this answer with 1 less vote. Feel free to suggest more reasons in the comments, or simply edit the post if you can.)         

Feel free to criticise.   

Answer 2

Arguments for no, don't copy SE: 

• One needs knowledge of the topic to upvote a certain post, too, even if he or she is just thanking.     
• Copying SE causes a default skew towards higher-voted answers and questions, which is not an accurate description of the post.  
• It's asymmetrical. Who doesn't like symmetry?    

(I strongly agree with this opinion, so consider this answer with 1 more vote. Feel free to suggest more reasons in the comments, or simply edit the post if you can.)    

Feel free to criticise.