In my opinion, the only advantage the third film has over "Quest for Peace" is that it was actually finished. I love Chris' scenes with Annette O'Toole, but everything else was ridiculous.
By contrast, it seemed the whole cast really wanted the fourth entry to reignite the creative spark of the original, but Cannon Films' greed got in the way. Gene Hackman actually came back since the Salkinds were gone, but the heroics sucked because of the severely slashed budget.
Story-wise, I actually prefer "Quest for Peace", but both of them are pretty bad.