I really don't understand why Toriyama put that statement in there. Clearly 18 wasn't having her hands full with Vegeta, and he was the strongest of the bunch. Piccolo showed he was completely incapable of even landing a hit on 17, who isn't much stronger than 18. Trunks admittedly got smacked from behind by 17, but even his direct sword slash was easily blocked and he was tossed into Vegeta, which fucking knocked him out. Three "Super Saiyan tier" players were handled without so much as an angry grunt from one of the androids. We saw later during the 25th Tenkaichi Budokai what 18 looks like when she's under pressure and scared, and she showed nothing resembling that sort of emotion when fighting Vegeta. At most, someone could argue she and Vegeta aren't terribly far apart due to a certain emphasis being placed on 18 "slowly pushing [Vegeta] back" because of his draining stamina, but that's about it. She still tanked one of his huge blasts with cosmetic damage at worst, and proceeded to tear him down like he was a sack of shit. He lasted a lot longer than Trunks, despite the two being in the same league, but that probably speaks more for Vegeta's durability than a big gap between them.
So, yeah, I don't think 17's statement holds a lot of weight when the fights themselves show the androids critically overpower the Z-Fighters.