I like Mass downloader... it is fast goes around 220KBPS in my dataone 500Home plan..
neways my suggestion will always be IDM because it gves me the option of shutting down the pc automaticaly once ur downloads are complete. also it is FAST..( most of them are actually)
in fact, almost all managers do provide this Shutdown when complete option..
so not an advantage for IDM.
One major advantage with IDM is that Rapid Share cant detect it.