I like Stargate too. In fact these days it's the game I'm playing. Though I go back and forth. For me, back in the day, I went from Stargate to Defender because the 7/11 got rid of their Defender and the Safeway on the next block got a Stargate :-)

What I noticed about Stargate back then, coming from Defender, was that it was easier to shoot things. I think this was because the Stargate chip was an upgrade--the faster CPU wouldn't steal time slices from me at odd moments, so the game was more predictable. I remember Eugene Jarvis and Sam Dicker talking about the Defender->Stargate upgrade process at the California Extreme arcade convention in 2014. Stargate is a fun game, and these days I play more casually, not really trying to perfect my skill.

As someone else in the comments noted: Defender is more raw. It's like those characters from the older version of the Matrix: Difficult to kill. It's like Yngwie Malmsteen's demo tape before his first album. There is a basic visceral appeal to it.