-c resumes download where left off, the rate limiting can be used to match the speed of your connection or intermediaries reducing stalls, drops and angry network users. I would often keep a list of URLs in `download-queue.txt` and use the above flags with -i to load the list of urls, letting it run overnight at some much lower speed.
A download manager would be fine if there was a non-opaque method of determining the download address, and they actually let you do that (I know the developer site for instance uses some combination of cookies/referrers to limit external access to binaries presented for download).