Differences between thermistors and thermocouples
Thermocouples:


wide range of temperature sensing (Type T = -200-350°C; Type J = 95-760°C; Type K = 95-1260°C; other types go to even higher temperatures)
can be very accurate
sensing parameter = voltage generated by junctions at different temperatures
thermocouple voltage is relatively low (4.3mV for Type T thermocouple with one end at 0 C, other at 100 C, so that's 43uV/C tempco)
mostly linear


Thermistors:


more narrow range of sensing (Quality Z thermistors spec'd at -55 to +150 C)
sensing parameter = resistance
usually very nonlinear
NTC thermistors have a roughly exponential decrease in resistance with increasing temperature
good for sensing small changes in temperature (unless you are careful in your signal conditioning, it's hard to use a thermistor accurately and with high resolution over more than a 50 C range).
sensing circuit doesn't need amplification &amp; is very simple (voltage divider with reference resistor tied to reference voltage usually is sufficient) – see my blog for more information about signal conditioning.
accuracy is usually hard to get better than 1°C without calibration