ahill1 said:
Well, she completely shattered Trunks' sword effortlessly, the same Trunks who was said not be too different from his father. If she weren't above Vegeta, how'd she be in a completely different league from Trunks?
Plus, saying she won't hold back isn't a whole proof if later evidence does suggest that. Kame-Sen'nin in the 22nd Budokai also stated he'd go all out against Tenshinhan once this latter saw through his multiple images technique, yet we're later informed he was still holding back. While the same wasn't stated for #18, that's inferable with how easily she took on someone on Vegeta's level whereas she was previously apparently fighting on par with Vegeta. So it seems suggested she was still holding back somewhat until Trunks butted in, in which case she decided to show her true self, which also makes sense with #17 stating everyone grouping up could be a threat to her.
Tenshinhan only says he'll use full power in Viz. The original dialogue has him saying he’ll get serious, which could be but doesn't have to be a synonym to full power:
Chapter: 124, P2.1-2
Tenshinhan: “Alright, I’ll fight you seriously just a little bit…!”
Kame-sennin: “Wha!? Are you saying you weren’t [fighting] seriously before?”
Chapter: Chapter 90, P.14.4
Context: Tao Pai Pai says he will fight more seriously, implying he wasn’t even at full power last time. Is it a bluff or is it true?
Tao Pai Pai: “This could be fun! I’ll go at it a little more seriously for once. It'll be good for my health!”
I think the blocking of the sword speaks more about her resilience than just power. Even an inanimate metal object made by Gero (His lab's gate) required the power of a Base Saiyan to be knocked down, so naturally an Artificial Human stronger than the Super Saiyan won't have trouble blocking and breaking a sword, or non-selling a powerful blast that should've hurt her in the case of Vegeta's blast earlier.
Kyo said:
They never look even unless you cherrypick panels which is almost what Trunks pretty much does.
Piccolo's statement is a bit weird and I feel like Toriyama just felt like he needed to throw in that infinite/finite energy distinction because it's a thing I guess. In the later chapters he clearly feels that the Saiyans are just weaker than the Androids strictly power-wise.
Even though Trunks watched like 90% of Round 2?
Other than the initial exchange after #18 got serious it's a pretty even fight. #18 lands a solid blow, but then Vegeta lands a combo and a blast that he says should've hurt her. Then they proceed to go toe to toe and Trunks makes his comment. Only after Piccolo makes the point about Vegeta's stamina that she truly gets the upperhand.
Trunks' statement could've not been made at all or could've been countered by Piccolo. Piccolo saying Vegeta's running out of gas doesn't need to be tied to the idea of Vegeta rivaling #18 by any means.
After Goku defeated Freeza the later was also treated as a joke even though they had a roughly even fight. The fights are more judged by their outcomes than by perfomances. And as you said, the Saiyans are just weaker than the Androids
strictly power-wise. #17 commented on Vegeta's fighting skills, which was the main reason Vegeta was able to keep up with #18. Power-wise he’s definitely weaker given #18 > Cell >= Vegeta.