>>29173612Speed and power wins. If they were matched on speed it'd be a toss up though.
Think about it man, in your scenario they have the same BST and HP. So it's assumed the attack and defense values are swapped basically.
For the sake of example, if Null has 50 attack and 100 defense, and Silvally has 100 attack and 50 defense, they will always do pretty much the same damage to each other if they use the same attack. Therefor, Silvally wins because it moves first.
Once you incorporate the item scenario however things get a little trickier. For the sake of ease we will use the same stats as above.
If Null has an Eviolite, it's defense becomes 150 instead of 100. But you specifically stated Silvally if holding the fighting memory. If it has multi attack, it gets STAB double damage which means Null would need well over 50% increased defense Eviolite grants to balance out the buff to Silvally.
tl;dr, Silvally wins both scenarios.
