Backticks having different output from $()

Question

The following code:

url="http%3A%2F%2Fstackoverflow.com%2Fsearch%3Fq%3Durldecode%2Bbash"

line=`echo -e ${url//%/\\x}`; 
echo $line;

line=$(echo -e ${url//%/\\x}); 
echo $line;

Produces:

httpx3Ax2Fx2Fstackoverflow.comx2Fsearchx3Fqx3Durldecodex2Bbash
http://stackoverflow.com/search?q=urldecode+bash

Shouldn't the `` and the $() produce the same result?