SPI vs I2C

Whats better to use with a PIC? I have been using a STAMP and two-axis MEMSIC accel that uses PWM. Now I am updating hardware to a PIC and all three-axis accels I find are either SPI, I2C or analogue out. I am familiar with doing the A2D. I am not familiar with either SPU or I2C. Any input/suggestions are greatly appreciated.
Thanks
Toby

I2C use 2 I/O, use the sensor resolution
SPI use 3,4 I/O, use the sensor resolution
ADC 1 I/0 10 bit resolution MAX

It's up to you, it's only different way. Tell us more about your whole hardware. Maybe there's some advantage to prefer SPI, I2C or A/D.