I use all three and Epic is by far the worse software. Their platform requires root access on machines. It starts up when I don’t want it. It acts like malware. It also pegs my cpu at 100% at unpredictable times and download lots of data.
It’s good that someone is fighting Apple and Steam, but I wish some better company would enter the fight. As it is now, I’d be sad if Epic won.
GOG is much better when it comes to games, although there are a very small number with issues (there is one they sell that is effectively only multiplayer and won't run without anti-cheat software installed, also GWENT is an online microtransaction thingy but there since it is made by CDPR). Almost everything works completely offline. The website isn't perfect but not that bad (quite a bit better than Bandcamp) and you can download from the website or use a client.
It’s good that someone is fighting Apple and Steam, but I wish some better company would enter the fight. As it is now, I’d be sad if Epic won.