I’ve used both. The external is really great if you fly commercially and just want to use for reference and also nice if you want to keep the stratux down on the floor or in a pouch while flying yourself. Additionally, if you get the external it will still work without the external antenna.

On a side note - I replaced the antennas with shorter less conspicuous ones and prefer that. They have kits on Amazon. Stratux ADS-B 3dBi Gain Small... https://www.amazon.com/dp/B07Z8FT94M?ref=ppx_pop_mob_ap_share

I would highly suggest doing this pieced together with the kit list on the stratux website and getting a gigantic external battery. It’s half the price and was a fun little project. The battery I have is 30000mAh and lasts a full 9 hour flight to Denmark and some even have solar panels built in.