You would also have seen people using voltage boosters. I use the VB as do lots of others.
Advantage for me is ,you have to charge the battery pack after every other run, VB fit and leave it.
Size the MJordan booster is small compact and has built it switch. As far as I know very reliable I have 2 and knows lots of people who run them with out problems.
They cost approx £35 I battery and charger about the same.
Why would you want to use both .???? Maybe some else will answer that one.
But Voltage booster for me ,runs perfect with the Tekin RS esc.