Why 'xargs bash -c' is far slower than 'xargs sh -c'?

Question

time seq 100 | xargs -i bash -c 'echo {}'

; 2.530s

time seq 100 | xargs -i sh -c 'echo {}'

; 0.223s

why?

PS: The title of mine for this post is more intuitive to be discovered or searched by google or any sort of search engines.