Sent Back the Pro-ject Turntable: What would be the best option in the $1800 range?

1200GR. 
Wasn’t sold on the looks at first but it’s a beast of a machine that will outlast me.

The Well Tempered Labs Simplex is a fine table.

Torque is not a big deal, once the turntable is up to speed, but the SL12010GR is just a much better product on all levels (motor, electronics, platter, plinth, etc), compared to the 1500.  I would add my voice to the chorus: go for the GR.

The 1500 is for noobs... the opener doesn't look like a noob

Thank you @noromance I stand corrected; SL-1200GR.
As per the OP's stated interest in the 'difference between' SL-1500C and SL-1500GR:
Premium Class DD TT / SL-1500C:
Starting Torque, 1.8 kg / cm.
Build-up Characteristic, 0.7 sec. From standstill to 33 1/3 rpm.
WOW and Flutter, 0.025% W.R.M.S.
Rumble, 78 db.
Platter, Weight: Approximate 2.0 kg Die-cast Aluminum.

Grand Class DD TT / SL-1200GR:
Starting Torque, 2.2 kg / cm.
Build-up Characteristic, 0.7 sec. From standstill to 33 1/3 rpm.
WOW and Flutter, 0.025% W.R.M.S.
Rumble, 78 db.
Platter, Weight Approximate 2.5 kg Diecast Aluminum.

Grand Class DD TT / SL-1200G:
Starting Torque, 3.3 kg / cm.
Build-up Characteristic, 0.7 sec. From standstill to 33 1/3 rpm.
WOW and Flutter, 0.025% W.R.M.S.
Rumble, 78 db.
Platter, Weight: Approximate 3.6 kg Brass and Die-cast Aluminum.
I must stand by my assertion though.
The two Models are directly comparable with similar specifications regardless of place of manufacture.
Both the SL-1500C and SL-1200GR use a Cast Aluminum Machined Platter with only a difference of 0.40 kg or Approximately 0.88 lbs difference in weight.
Notably Technics listed Specification shows Weight (Including Turntable Sheet) for SL-1500C and Weight (Including Rubber Sheet) for SL-1200GR.
This would connote a difference in material perhaps.
With the SL-1200G (Also listed by Technics as Grand Class) using a Brass and Cast Aluminum (combined) Platter being 0.8 kg or 1.76 pounds heavier than the Platter used in the SL-1200GR.
Obviously the SL-1200G has better Damping as suggested by comparison to the Reference Level SP-10R Truely 'High End' (i.e. "Separate Control Unit") with a Price to match BTW.
As to the comparison of the Design of the ' Motor Structure ' between the two TTs in question.
The Technics web-site ( https://www.technics.com/us/products/premium-class/direct-drive-turntable-system-sl-1500c.html ) clearly states: ( for the SL-1500C Premium Class DD TT )
"The Latest Coreless Direct Drive Motor Achieves High-precision Stable Rotation"
Further Stated: "The motor exclusively tunes the single-rotor, Coreless direct drive motor adopted by the SL-1200GR" and also references: "technologies acquired through the development of the SL-1200 Series and the high-end SL-1000R" with: "lavishly inserted into the motor drive unit, a key part of the turntable".
Further note: A Graph (Damping Charcateristics Graph) comparing Damping Performance for SL-1500C which would help clarify and delineate differences is not provided in the description. As it is provided for comparison for both Grand Class Models SL-1200GR and SL-1200G.
And to add to all the excitement.
The Tonearm Specs appear to be the same for all three ( SL-1500C / SL-1200GR / SL-1200G )DD TTs. The SL-1200G has
Perhaps suggesting that the Same Tonearm is used on all three Players of distinct and separate classifications ( Premium / Grand ).
Anyone wishing to dispute this particular 'unconscionable' Claim with facts or knowledge backed by facts feel free to jump in here.
>>>                                                                         <<< (provisional)
Again from the description of Premium Class SL-1500C:
"Simple Design with Functional Beauty"
And:
"The SL-1500C sports a simple design without unnecessary frills, while retaining the superb operating feel that is a Technics tradition. The attractive appearance lets you enjoy playing records to your heart’s content.".　
In Summary.
The Premium SL-1500C is a 'Dynamite Grade' High Value Player worthy of consideration.
My argument is not that the SL-1200GR is not a great TT. Certainly of higher Specification.
I would however argue against the Slide Adjustment for Speed Control.
It would seem to me to be extraneous and relate more to the lines historic Professional (aka DJ) market placement.

However I would favor the Strobe ( for visual verification and appearance ) and Queuing Illumination. Very nice feature for a Manual TT!
Yes. I think that "Torque" is significant with regard to Stability and Precision for operation /
function of the DD TT.
Reference:
"High-precision Motor Control for Ideal Rotation Conditions", "rotation control, which verifies and corrects the precision of the motor".
My intent is only to offer an option for the interest of the OP.
More to the point.
Who here would argue that a step up to the upper Tier of the 2M Series would not be possible or beneficial (SL-1500C)?
Execution Squad, What say ye ...