Buying a new TT today

Either one will get you another huge step up. So which one is best has less to do with how much improvement you will hear (massive either way) and more to do with your long term plans and goals.

For example, say you get a great cart like the $1500 Soundsmith Zephyr MkIII https://www.sound-smith.com/cartridges/fixed-coil/zephyr-mk-iii A great long term choice that allows affordable re-tipping. Huge improvement now and another huge improvement later if you upgrade to a better table and keep the Zephyr.

Then when you upgrade the table you can focus on the table and arm and get better. Whereas if you buy a better table now you have to accept a package with a cheap cartridge, sort of right back where you are now only at a slightly higher level. 

Either way you will hear huge improvement. I just think that with turntables you're really buying four separate components- table, arm, cart, phono stage. The sooner you can separate and start dealing with each on its own the bigger and better your long term results will be.

A new quality cartridge is just your first step down that path. 

Turntable. You will recoup a lot more for your Debut Carbon than you might for your cartridge.

You will need to listen carefully as any potentially huge improvements on your Pro-Ject deck will be hard to find.

The price of turntables and associated gear hardly have a limit. Thankfully sound quality tends to taper off quite dramatically once you reach the likes of the Technics SL1200G etc.

If you can't reach that you should still see a decent step up from the Debut Carbon with the standard SL1200GR plus decent cart and be able to offload your Pro-Ject plus Ortofon 2M Red etc into the bargain.

https://www.stereonet.co.uk/reviews/technics-sl-1200g-turntable-review

Are your plans to keep, trade or sell your existing Pro-Ject TT?

If you have Technics dealer make sure to check this turntable at some physical store, some people just don't understand what it is looking at the pictures online. You have to touch it, press start and stop button, put the needle of the record, adjust the tonearm ... and you will understand why this turntable is so good. Technics SL1200GR (in silver or black) is what you can buy quickly and easily. 

Ortofon M2 Red is an awful cartridge, it's entry level, forget about it. 

On Technics tonearm you could use many mid compliance MC or MM or MI, you can also use high-ish compliance cartridges (MM/MI) and if you will mount something like Victor X-1IIe you will be blown away, i'be been using this vintage MM on my Technics EPA-100 tonearm and it was shockingly good compared to many cartridges. Audio-Technica cartridges like AT-ML170 is amazing, actually many AT cartridges are great. I'm huge fan of Stanton and Pickering top of the line models like SC100WOS, XSV/4000, 5000, 7500.... stunning for Technics tonearm. Also Grace LEVEL II Ruby 

Turntable. You will recoup a lot more for your Debut Carbon than you might for your cartridge.

If the goal is to sell what you can get the most for, then maybe. I thought it was to get the most sound quality? I would hang onto the cart in order to have a virtually new cart to sell with the table. Most people at this price level are looking for a complete package. The table will be worth more as a complete package with the original cart. 

You will need to listen carefully as any potentially huge improvements on your Pro-Ject deck will be hard to find.

So, purely as a learning experience, does it really make sense to recommend upgrading a turntable, then immediately saying but it probably won't be worth it as any improvement will be hard to find?