Can't resist jumping into this thread, as I'm such a big fan of both Yamaguchi and Gordeeva.
I actually think Kristi/Rudi were very well-matched in 2 specific ways. 1) They were obviously both very strong individual jumpers. 2) They were stylistically similar. Both had a lot of refinement, attention to detail, and musicality in their skating. Both were rather elegant, polished, almost delicate skaters. So in this way, they matched well.
Areas where they weren't as strong: 1) Lack of a big height difference. 2) Opposite rotators. 3) Neither of them were known for their speed. At that time in pairs, speed was one of the biggest factors in winning. That was definitely their biggest weakness as a team IMO. 4) They only had one triple throw, at least in 1989 and 1990, when their layout included throw triple Salchow but only throw double loop. (Whereas G/G had throw triple Salchow and throw double Axel.)
A brief glance at a couple videos from the 1989-90 season illustrates the difference between Yamaguchi/Galindo and Gordeeva/Grinkov at that point.
Yamaguchi/Galindo Nationals 1990
https://www.youtube.com/watch?v=QFthnJ6xg9k
Gordeeva/Grinkov Europeans 1990
https://www.youtube.com/watch?v=gSL-hpsFAtw
Gordeeva/Grinkov were evidently faster than Yamaguchi/Galindo and had bigger amplitude in their pairs elements (twist, throws, even lifts). Artistically, they were just a little more developed and sophisticated, with better unison too. Yamaguchi/Galindo were much superior side-by-side jumpers. However, I think in that era, the judges didn't care about side-by-side jumps nearly as much as they cared about speed and pairs elements. Hence, Gordeeva/Grinkov's advantage.
Despite this, however, I still feel Kristi/Rudi were a very talented pairs team, as shown by their 5th-place finishes at Worlds in 1989/1990. They're definitely one of the great "what ifs" of American pairs skating. Who knows what would have happened if they had kept going, or if Kristi had ever devoted herself full-time to pairs.