Zwift is all about power output, so if you’re interested in competing against others, then whatever gets you the most power. There is also the game aspect of it, so the more you ride, you get perks like aero carbon wheels, things like that, that will let you go faster. I tend to ride Zwift on a (virtual) steel bike with the box section wheels and a Molteni-esque Jersey because, hey, that’s how I roll. My actual bike that I ride is my old TT bike because it otherwise doesn’t get much use.
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N = '96 Colnago C40, '04 Wilier Alpe D'Huez, '10 Colnago EPS, '85 Merckx Pro, '89 Merckx Century, '86 Tommasini Professional, '04 Teschner Aero FX Pro, '05 Alan Carbon Cross, '86 De Rosa Professional, '82 Colnago Super, '95 Gios Compact Pro, '95 Carrera Zeus, '84 Basso Gap, ‘89 Cinelli Supercorsa, ‘83 Bianchi Specialissima, ‘VO Randonneur, Ritchey Breakaway Steel, '84 Paletti Super Prestige, Heron Randonneur