If anyone wanted to know what the difference between the two variants really is, here's a comparison.

Obviously the pink graphs are the OCXO. The difference is remarkable. That's what the extra $100 buys you. Again, everything about the circuitry of the two is identical, except for the oscillator itself, the oscillator power supply (an LDO for the TCXO and a buck converter for the OCXO), and one resistor that adjusts the scaling of the DAC output. In the firmware, the slow time constant for the PLL for the DOT variant is 100 seconds instead of 200 for the OCXO (because it's not stable enough for a slower time constant than that), and there are a couple of constants that change because of the varying control voltage slope between the two.