For example, OpenWRT allows more control over DNS settings. There is no user access to /etc/hosts or /etc/resolv.conf on iOS/Android. User can easily run servers on the e750, e.g., DNS or proxies, and inspect the contents of traffic, including TLS. The e750 has fewer limitations when running servers on Android with something like Termux. Using Termux, it is difficult if not impossible to run essential programs like tcpdump. Moreover Termux is not available for iOS. iOS is intentionally "locked down" and Apple prevents users from compiling iOS from source.
The e750 can accept CAT5/CAT6 Ethernet cables. Wired internet is an option. "Smartphones" are wireless-only.
Corrections welcome.