The biggest thing the pre-Kai dubs of Spain have going for them over the Latino Spanish dub is their handling of insert songs (especially the Catalan dub apparently). Aside from that, the Latino dub is considered far better than the Spain dubs til Kai (Catalan, Galician, Basque) and Battle of Gods (Castellan, Valencian), where things start to even out (there was never a Castellan dub of Kai nor a Valencian one).
What was wrong with the Spain dubs pre-Kai? For one thing you have a vastly inferior script for large chunks of the series thanks to reusing the French script as it's base. The French script that has an aversion to naming characters. The French script that almost never calls Goku "Kakarot" or similar. The French script that renamed Piccolo to Satan Little-Heart and the Saiyans into Space Warriors. In fairness, starting with Kai the French dub was improved massively and much of that crap was abandoned. The Castellan dub followed suit, but to this day the modern Catalan, Galician, Portugal Portuguese, and Hungarian dubs keep many of the old French derived terms.
Even aside from that, the screams of at least some of the pre-Kai Spain dubs were either weaker than the Latino screams or literally copied over from the Japanese.
Here's a chart (notice how, of the five languages of Spain, Castellan got the short edge of the stick by returning to the French scripts after a period of not using them)
For some context on that chart, the Spain dubs started close to the same time as the French dub. There may or may not have been a brief hiatus after DB ep 26 (don't remember the details) but starting with Ep 27 they took directly from the French script. This lasted until Z Ep 105, when the Spain dubs got ahead of France, and had to translate the scripts more directly. I wouldn't be surprised if the switch in scripts increased the script quality. Most of the Spain dubs used more the direct materials for the rest of their runs, but the Castellan dub entered a second hiatus, and when it ended, it took from the French instead of the Japanese.
As for the Latino dub, it's a little complicated. The first Latino dub was based off Harmony Gold's ill-fated English dub (complete with lots of name changes) and was relatively more successful than it, going up to 60 episodes. The second, much more successful dub, redubbed the first 60 episodes and then switched studios (though keeping the same cast more or less) and covered the rest of the series as well as Z and GT. The second dub post studio switch is considered one of the most accurate pre-Kai dubs of the whole franchise, much more than the pre-Kai dubs of Spain. As for the redub of the first 60 episodes, I'm not sure if the scripts from the first dub were reused or not, but, for the most part, the names certainly weren't.