Zwift is undoubtedly the most popular but is less of a training platform, more of a social computer race/ride game. It will ultimately come down to your preference. The Sufferfest and Trainer road are purely training platforms aimed at performance gains, one with videos/music and comedic interjections.
Ultimately it will depend on what you prefer, I think they all offer trials so probably best to try a few if you are unsure?
Ultimately it will depend on what you prefer, I think they all offer trials so probably best to try a few if you are unsure?