pick the most stable one ( it will have a lower stability #)
newer ones are rated at +- 1 Mhz
good ones ar rated at +- 500 kHz
real good ones are rated at +-250 kHz
the lower stability you go the higher the price
a lot of people watch the noise level ( or temp level) and think just because its lower its better, this isn't always true.
a higher temp and lower stability lnb might produce lower signal #'s but will have a better stable picture in most cases.
1) precision gold label series highly stable 15 deg
2) eagle aspen 17db
3) chaparral 20 deg = +/- 2.5 MHz