A short to medium range airliner with a design featuring rear fuselage mounted engines, a T-tail, moderately swept wings and seats for around 100 passengers.
Am I talking about a CRJ-1000 . . . or a DC-9 30?

I got these range and capacity #'s from various sites on the internet, including Wikipedia. They're all ballpark, nothing more needed here.

Cruise and range:
10 – long range cruise 478kt. Range with max payload 570nm.
30 - long range cruise 430kt. Range at long range cruise with 80 passengers and reserves 1670nm.
40 - long range cruising speed 443kt. Range with 87 passengers and reserves at long range cruising speed1555nm.
50 - Range at long range cruising speed with 97 passengers and reserves 1795nm.
CRJ-700 – Long range cruise 442kt. Range with max payload and reserves 1685nm.
CRJ-900 - Long range cruise 442kt. Range with max payload and reserves 1596nm.
CRJ-1000 - Long range cruise 442kt. Range with max payload and reserves 1491nm.

Capacity:
10 - Seating for 80 in a single class.
30 – Seating for 105 in a single class. (32” pitch)
40 - Seating for 125 in a single class. (31” pitch)
50 - Seating for 139 in a single class. (31” pitch)
700 - Seating for 70 (31” pitch), though I’ve read elsewhere it can seat 78.
900 - Seating for 88-90 (31” pitch).
1000 – Seating for 100 (31” pitch).

You really don’t think an aircraft with certified seating for 105, cruising speed of 430, and range of around 1600 nm’s competes with an aircraft with certified seating for 100, cruising speed of 442, and range of around 1491 nm’s?

The DC-9 was originally developed as a certified 80 passenger jet with a max payload range of 570 nm, about the distance from MSP to MEM. Assume it doesn't fly full (nothing did in the late 60's), you fly 55 passengers or so around 500 nm's. Sounds like the original mission of the CRJ-200, huh?

To me, they sound almost identical, the DC-9 30 and the CRJ-1000. And that's why it is essential that they be flown by the same pilots, mainline pilots.