now only one difference between any board - is a available pins count.
Sparkfun[promicro] - total 18 pins, and 9 can be used for internal(onboard ADC) axis.
Arduino[leonardo] - total 23 pins, 11 internal axis.
Arduino[micro] - total 24 pins, 12 internal axis.
PJRC[Teensy 2.0] - total 25 pins, 12 internal axis.
JRC[Teensy 2.0 ++] - total 46 pins, 8 internal axis.
so if you want more axis, you can use SPI connected external ADC:
a) "kma200" magnetic field angle sensor + 13 bit ADC;
b) "MCP3201" 1 channel 12 bit ADC;
c) "MCP3202" 2 channels 12 bit ADC;
d) "MCP3204" 4 channels 12 bit ADC;
e) "MCP3208" 8 channels 12 bit ADC;
f) "MMSENS(MCP3202+KMZ60)" magnetic field angle sensor KMZ60 + MCP3202 12 bit ADC + trigonometric math at controller, my new project digital sensor;
SPI is a very easy to use, just connect power and ground from controller to ADC and connect SPI lines MISO/MOSI/SCK and CS(chip select). pin "CS" are individual for ADC, other pins is common for all ADC's connected.
PS: here some pictures of "MMSENS" working.