this all depends on your supplier. I have 3 suppliers one is able to get me 90% of all sly channels plus international channels, like pakistani indian greek french canadian etc etc but the channels will often not work or become unstable, the other 2 are more uk and sport centric and have been extremly stable since jan 2017. I have 3 separate providers as a back up. you will never really be able to fully replace all the the sly listing with iptv as the infra is just not good enough. but 70% availability is still good enough for the time being.
At the moment i have a zgemma box with a sly line installed. I have added my IPTV subs manually to the box without channel numbers or epg. Any channel i cant get on the line il pick up on iptv as well as all the HD channels. and ppv events.
It all come down to what your after while managing your expectations as IPTV is still in its youth and needs time and investment to mature and become stable...