Should I keep the Turntable or sell it?

OP
One way you could also look at the price difference is that you are getting more tt for your money with the Clearaudio.
You can always upgrade the cart later.
It would indicate to myself that the Marantz could be less of a table and it's the cart that is the bigger star there.

As stated the Clearaudio is a more modern design.

I know which way my money would be going here.....

Yeah, definitely what uberwaltz just said.

The leeway in my prior statement is in what constitutes a "reasonably good deck". I've heard the Concept (even with the cheap Concept MM), and I think that table just makes the cut. I'm not so sure about anything else in that price range bundled with an arm & cart as a package. I'm not so sure about the Marantz model - and if it were my money I'd definitely go with the Concept over it. Clearaudio (mostly) nailed it with their present lineup, which you can see given their popularity and longevity. 

I'd also be giving the new Technics decks a look, though I have no experience with them. I think they're pretty interesting. 

Cartridges are wear items, and they can be easily destroyed with a simple accident. I say go a bit further with the table/arm/phono before you experiment with more exotic cartridges. THEN the arm/cart quality & matching will absolutely be the most key determinant to your resultant sound quality, you may wish to explore MC cartridges, etc. 

@best-groove

...it’s okay to get them but not inside a turntable for problems that could trigger.

Wait, I am not following then. If you are saying having a DAC, Bluetooth, Phono Stage (it doesn’t have USB, btw) all in a system, then what is the difference if they are insulated inside of the TT VS sitting beside the TT? Assuming they are good quality (CA has made great products for 50 years), why would it matter if they are inside the unit? Are you talking about RFI, because unless I put them in another room, there will still be interference, and I trust a Cambridge Audio engineer to build and place these components within a system, than I would ME placing them in various parts of a room. Maybe I just don’t understand your POV, though.

(Rant about audiophilia coming)
One thing that I find fascinating, is that audiophiles hate the idea of multiple components inside a singularly engineer product, and think they can always "al a carte" their own systems better then a company doing this stuff for 50 years. KEF LS50 Wireless speakers are another example... many audiophiles that I have conversed with hate the idea of not being able to match their DAC and amp with their passive speakers, and I understand personal preference, but if a technology that is so great and award winning (KEF LS50) why not trust the same engineers to pair the right DAC and amp? I feel like ego tends to get in the way of things sometimes, and non-experts believe they know better than the folks they pay huge sums of money to for the individual components.
(Thanks for the therapy)

So my personal hypothesis is... A company who has been in the business for decades and who partners with other companies who deliver great components, is very likely to be capable of engineering and compiling a turntable, arm, and cart (package) that is specifically engineered to sound great together. Isn’t this exactly what Apple did and continues to do very successfully with the iPhone? It is an all in one solution, built to be completely integrated and services it’s own ecosystem of applications. Luckily and hopefully, I will have years to test this hypothesis and see if I can prove it null.

I appreciate the information everyone!

@bignamehere

Sorry I explained myself wrongly; what I wanted to say is that bluetooth or usb or power supply switching do not have to coexist in a TT but not even attached or close to a stereo system that wants to be low, mid or hi-end; these features may be fine for multiroom systems or where it doesn’t matter to listen to music in the best way. IHMO

@best-groove I think I’m following... maybe. No, those components don’t need to be located in a system at all. It seems what Cambridge Audio is predicating is that the future of hi-fi analog is digital, or more than there is a larger market for those wanting all-in-one systems that are mid-range in quality from a hi-fi perspective.

if I had the money, sure I’d just buy all separate components and place them far away from the table as possible. I would also probably buy different components though for analog and digital and have two separate systems. Not in my budget though, unfortunately.