as far as its comparison with 327 is concerned.
This is a next level.
ELM 327 works with phone. so you need to connect your phone all the time.
for fuel calculations and calculation of
"Distance to Empty" or "Range"
is concerned, ELM doesn't keep the history of previous readings.
where as this is full time connected device and keeps the history as well.
This has its own display with auto brightness features
This has alarms that you can set to any gauge. for example when water temperature exceeds 100 'C we ca set sound alarm
etc etc etc