Based on what I've seen, Magnus the Red is stronger and more durable.
Funfax: Horus didn't just continue bombing Isvaan III after Angron, allied Primarch of the World Eaters, stupidly landed and brought the fight to the ground, because razing a planet would just piss off a Primarch.
Konrad Curze as a baby was sent through a planet's adamantium crust to its core, and crawled right the **** back out.
Speed is iffier, but Magnus has telepathy to read her mind as well as precog. Sanguinius should have at the bare minimum triple digit reaction-time (Perceives supersonic projectiles as nearly still-moving), though where Sanguinius ranks among Primarchs speedwise is unknown.
Oh, and Honorius, merely a Space Marine, could note the positioning of a Word Bearer, where his weapons were holstered, his posture, his armour's structural weaknesses, how to best shoot and incapacitate him without rupturing the thin vessel they were in and introducing him to the void, and shit... All in less than a nanosecond.
Argel Tal, another Marine, who in The First Heretic can't even perceive a Primarch while he is fighting, is capable of flying (With his jump pack) and dodging arcs of electricity fired from a xenos weapon.
Oh, and Daemon Primarch Magnus? Lulz.
He can casually dissipate a planet-razing spell as a Daemon Prince.
Also, taking all of Magnus's luck would prove to be a fatal move. Since he has negative luck, lol. Tzeentch loves to **** over his most powerful pawn.
Oh, Magnus can also kill with a glance. He glanced at hundreds of Space Wolves, and hundreds of Space Wolves died.