Honest question about cartridge vs. turntable performance.

The answer is it depends on how terrific the cartridge- and how terrible the turntable.

The obvious answer is the question itself is terrible.

There really is no difference in terms of pure performance. For every $2500 or whatever on a cart you can find $2500 in a turntable that will be a virtual tie in delivering sound quality. Where the difference comes in is over the long term. Your $2500 (or whatever, numbers aren't the point) cartridge will in 5 years (or whatever, numbers aren't the point) be worth zero. Your $2500 turntable on the other hand will be worth, well who knows? But not zero! Could even be worth more. You never know. Point is, one is a consumable, and one is not.  

So in my book if you are gonna go big it pays to go big on the table. Because then in five or ten when you replace the starter cartridge the better one you buy will be going on a better table. Where if you spent the money on the cart the next cart will be going on the lesser table. 

So these questions are like games where only Kirk (as played by millercarbon) knows enough to reprogram the game to win the no-win scenario.

How much difference does a turntable really make compared to the cartridge?

A lot.

Will I hear a significant difference if I upgraded my turntable and kept the same cartridge?

Yes.

Isn’t the cartridge 90%+ of the sound from a vinyl setup?

Yes. It is. The turntable is only 90%. Oh, and the phono stage. A good phono stage is 90%. At least. Tone arm, 90%. 

By my count that's 360%- which coincidentally is exactly how much better analog is than digital.