We have a crawling engine that uses curl and caters to about 400,000 ppl / month. Although curl supports concurrent downloads, it does not support bandwidth limiting ( only in php 5.4.0 ) which is why my boss wants me to move to aria2. He also says Aria2 is faster ( which seems to be true to me as well )
Aria2 would require a large amounts of changes to the system. Right now we have crawling system which does not crawl in a conconrrent manner.
Would moving to aria2 be a good decision?