At what point do you abandon ranking up your 4* champs?

I'm in that point where I am making the transition to 5* champs, but so far haven't really pulled very many "good" ones. I know I should be saving resources for those, but I'm still seeing more value in my 4* roster. This is more due to the fact that duping 5* champs is so much harder to do. Do you rank up a 5* champ with the hope that you'll eventually dupe him? Or the 4* champ that will be more useful now?

For example, with my science champs I have the following options:
4* Quake to R5
4* WW2 to R5
5* OG Spidey to R3
5* Miles Spidey to R3

Both of my 4* Champs can be thrown into the mix right now, whereas I'll be waiting to dupe my 5* champs before they're even useable.

Thought right now is to rank up Quake and Miles.

But the overall thinking is applied across the rest of my lineup. 4* Rogue vs 5* Nightcrawler, 4* Medusa vs 5* Drax, 4* Magik/Dorm vs 5* Hood/Voodoo.

All of that being said, I'm already sitting on 9 other R5 4* champs (Gwenpool, AA, Guilly, Hype, Spark, X23, Switch, Hulk, & Vision).

Doesn't seem like there is a wrong answer, but would definitely like some help with which is "more right"...