For you my man. Taking from the guide.
"Trading attacks in SFV works differently than in SFIV. If two grounded non-specialmovesclash (more precisely, if both characters’ activehitboxes collide with each other’s hurtboxes on the same frame), the player using the higher-strength button wins the exchange and is rewarded with a clean counter-hit. So, if Ryu’s standing hitbox connects with Ken’s hurtbox while (on the same frame) Ken’s standing hitbox connects with Ryu’s hurtbox, Ryu will be counter-hit (and in this case, Crush-Countered). It’s just as if Ryu was interrupted during his attack’s startup, even though his standing was active and well-aimed. If Ryu used standing instead in this scenario (or if Ken used standing /), both characters would be put into hitstun since their attack strengths are equal. An actual trade occurs.
Trade priority is: Throw > Heavy > Medium > Light
This altered system mechanic has several consequences for gameplay, coming from SFIV:
You can no longer trade your heavy attack with a light attack in order to recover before your opponent’s longer hitstun and follow up with a combo. This type of “trading up” situation was common in SFIV, but in the same situation now, you counter-hit your foe cleanly.
Medium- and heavy-strength frame trap attacks are more attractive than quicker, weaker frame-trapping lights because you essentially get an extra frame to counter-hit someone who is retaliating with light attacks. They can’t just call a trade a draw, and they must rely on their speed advantage. You wipe this out if you use medium-strength frame traps with only three- or four-frame gaps.
With certain characters, there is more of a rock/paper/scissors game when playing footsies when you’re taking trade priority into account. For instance, you may be more reluctant in challenging Chun-Li’s hop kick with your standing or pokes, unless your goal is to interrupt her before her first active frame.
This priority system applies to grounded normals and grounded unique attacks. It doesn’t apply to jumping attacks, nor does it apply to special moves. If a special move or jumping attack is involved in a trade scenario, they will simply trade as normal, with both characters entering hitstun. Note finally that throws will win over strikes if they clash on the same frame. "