What are the differences between iputils-ping and inetutils-ping?

iputils’s ping supports quite a few more features than inetutils’ ping, e.g. IPv6 (which inetutils implements in a separate binary, ping6), broadcast pings, quality of service bits... The linked manpages provide details.

iputils’ ping supports all the options available on inetutils’ ping, so scripts written for the latter will work fine with the former. The reverse is not true: scripts using iputils-specific options won’t work with inetutils.

As far as why both exist, inetutils is the GNU networking utilities, targeting a variety of operating systems and providing lots of different networking tools; iputils is Linux-specific and includes fewer utilities. So typically you’d combine both to obtain complete coverage and support for Linux-specific features, on Linux, and only use inetutils on non-Linux systems.

inetutils-ping is the portable GNU implementation, which is used on non-Linux Debian systems (such as Debian GNU/kFreeBSD).

iputils-ping is Linux only, but does have more features. If you are using Linux, you probably want iputils version of ping.

iputils-ping performs DNS reverse lookup via PTR query. You will have to wait for a timeout if there is no response from your DNS server.

inetutils-ping performs way more better in this situation.