Type: Null vs. Silvally?

I've got an Adamant natured Type:Null here with me and I'm not sure whether I should evolve it or not. Statwise, Null has a horrible base speed, but we can fix that with Flame Charge which boosts speed by one stage. Ability wise, it is immune to CRITS which is just amazing and makes it fit the bulky physical sweeper role even better. Its got a decent move pool. Slap an Eviolite on that thing and its Defenses skyrocket. EV train Null 252 HP and 252 Attack and your basically set. But then I thought to myself, how can I pass up Silvally's RKS System which allows it to go god mode and change its type. And let's not forget Parting Shot which is basically an upgraded version of U-Turn, lowering your opponents Atk and Sp.Atk by one stage and allowing you to switch out. Plus Silvally has a base of 95 in speed meaning it's fast enough to outspend most Pokemon and has a better movepool than Null. That's where you guys come in. Should I evolve my Null to Silvally or keep it as is. Which would you vouch for and say is more viable for competitive play out of your expierences? I just recently beat the entire game so I've got no clue.

I'd say that Silvally is still the better choice. I don't know how bulky Eviolite Type Null would be, but i'd think that it's likely to not be terribly amazing, as it lacks a non-Rest recovery move, and base 95 is rather average for most stats these days. Generational changes have slowly been making defensive 'mons and teams less viable as well.

With Silvally you at least have not completely garbage Speed, and it's more flexible given it's better movepool and ability to be whichever type it wishes.

Silvally > Type: Null. As the above already mentioned, Silvally's RKS System allows it to be any type while holding a Memory. IMO, Silvally's Parting Shot access outweighs Null's Eviolite-boosted defenses; Porygon2 does the bulky Normal thing better.

From an in-game standpoint, you really should evolve your Null, since it's the only one you get in the game outside of trading. If you're crazy to train Null up to 100 without evolving it, you can't evolve it at that point anymore, missing your chance to get Silvally.