I use both of these for last 3 years, and these work OK.
For running both dump1090 and dump978, you need these 3 steps
(1) Plugin two dongles into RPi
(2) Serialize these two dongles by 8-digit serial numbers 00001090 and 00000978
(3) Configure piaware:
–(a) Enable 978 by setting: uat-receiver-type sdr
–(b) Add serials numbers of both dongles to piaware config