how accurate do you need the 32KHz for a real time clock?

RC oscillators are not accurate.

Sorry,

I may have been misunderstood. I am referring to two topologies for crystal oscillator. Not RC vs. Pierce.

Using the crystal at 32kHz, which topoloogy is advantageous for power consumption and start-up time:

1. Pierce oscillator with crystal
2. Differential Relaxation oscillator with onchip C it has cross coupled NMOS with current sources and the crystal is connected across it.

ic_engr