The purpose made IPTV boxes are a three part system only one of which is the box itself. Infomir MAG boxes were the best IPTV systems because they incorporate Stalker middleware as does a Z8 or buzzbox which all connect through a portal. IPTV suppliers will never stream above 50fps 1080 which the purpose made boxes easily cope with.
The second part of the system is the pre loaded software and MTVOL2 is unbeatable but has been cloned.
The third part is the dedicated remote control, a Buzzbox has dedicated buttons on the remote for record, pause, rewind, VOD, Server, Recordings, LiveTV (same as MTOL2) last prog, EPG, TV series, category with four coloured buttons which can be dedicated to apps such as VPN.
The EPG from IPTV suppliers is loaded into the RAM. so for fast zapping 2MB works well - a BUZZ XRS 4000 has 4MB.
These things are custom built IPTV boxes designed from the ground up. Everything else mentioned has been designed for something else so is therefore part of a homebrew system.