We have both, the VM side is c/s so uses little internet, runs smooth with very few problems, can record with timers/series links, receives everything from VM however SS no longer has HD so its SD only on SS. You dont get any VOD & not ALL PPV events are shown on VM but for us its still the strongest most stable way to view channels.
On the IPTV side we get far more than on VM, a huge VOD section, more sport (US/CAN) channels than you can shake a stick at, 3pm kickoffs, iFollow, ALL PPV events, IPTV is not perfect & can have problems recording, see some motion blur on fast moving images like sports & you might/will need to run a VPN to avoide enforced blocking. Lots of niggles with IPTV but on the whole its watchable but will require more effort keeping things running. IPTV is continuous internet streaming unless you have a Sat cable connected & switch the box to a Sat fta channel when not in use.