High-order explosives can detonate at rates far in excess of 100 m/s. TNT, for example, has a listed detonation velocity of 6900 m/s.
Minor Scale was a test in which 4.8 kilotons of ANFO ws detonated to simulate the effects of a nuclear blast. Based on a density of 840 kg/m^3, that’s a sphere of ANFO 22 meters across. With ANFO’s detonation velocity of 3200 m/s, if detonation was initiated at the center of the sphere (assuming the initial form was indeed a sphere) the entire mass of ANFO would have detonated in about 3 milliseconds.
TNT is twice as dense as ANFO, so a 50-megaton sphere of TNT would be about 17x as large, i.e. 381 meters in diameter. With its higher detonation velocity, the entire sphere would be detonated in about 28 milliseconds. That’s considerably slower than the nuclear reaction that took place in the Tsar Bomba, but plenty fast enough to generate a ridiculous blast wave. The 50MT nuke releases a whole bunch of thermal energy and relies on the surrounding atmosphere to intercept it, heat up, and expand accordingly, but a lot of that released energy doesn’t get intercepted by the atmosphere - just gets pissed away into heating up solid surfaces that have a view of the blast. The Sphere-O’-TNT, OTOH, initially dumps all of its energy into a particular 50MT of gases, the products of the detonation reaction.
Except for very close range, I’d expect comparable damage between the two blast events.