Completely incorrect, gecko
Type null has an extremely limited movepool, and the only way you'll be outperforming silvally is with eviolite boost, which would be a waste of time due to type nulls extremely limited defensive capabilities, with no defensive stat boosting moves type null can only offer little damage when built defensively, only useful for toxic stalling. and that's a huge discredit to this lines abilities
Silvally is meant to be a multi-brand sweeper, being able to take any position, a steel type silvally is going to be equalling null in most areas of defense and offers much more coverage do defend itself. Silvally can also take a much better special sweeping position with it's huge range of coverage options. You can keep your Type: Null, I'll be using it's superior evolution