Finn can't keep up with her.
Sure he was the quarterback and the Glee male lead (only because Finn joined Glee before he did, Puck thought) but Rachel was determined. Unstoppable. Incessant.
She'd go on about Broadway musicals and the Tony awards with her mile a minute mouth and honestly, he doesn't think Finn's innocent, I-believe-I-got-my-girlfriend-pregnant-via-hot-tub brain could process it all. She could dance the hell out of Mike Chang and belt out show tunes to boot. She'd just get bored with him. Eventually.
And yeah, maybe he had the smile of morning cartoons and the attitude of a confused little boy which may be attractive to some girls who still weren't over their Barbie and baby doll phase. He'd acquiesce not only to Quinn's every whim and desire (especially now that he thinks that she's knocked up with his kid) but to Rachel's too. He enabled her. He'd return those smiles and greet her with that annoyingly goofy voice and knock her out with his high B.
And well, it wouldn't take a genius to figure out how Finn was in bed, given those characteristics and the fact that his girlfriend (under the pretense of wine coolers and self esteem issues) had sex with his best friend and not him. He couldn't handle Quinn; what more incessant, determined Rachel? Her kisses were hungry and her hands were just all. Over. The. Place. She was kind of rough and demanding and it would take someone equally (if not more) rough and demanding (and experienced) to stay up to par.
That someone was sure as hell not Finn Hudson. It was football stud, motherlover, serenader extraordinaire Noah Puckerman.
And he saw that she hasn't forgotten it. Whenever Finn and Rachel did their choreography, she had to adjust to his rhythm. She had to position herself properly against his body. She had to appropriate her grip with awkward smiles and avoiding glances.
Which almost always landed on him.
And he would smile at her and lick his lips. She would blush and look back up at Finn and then screw up her choreography. He's sure everyone would chalk it up to 'she's attracted to Finn and it's awkward', but only he knew the real reason.
Rachel sat back down as Mercedes practiced her solo. He moved closer, their arms touching, his presence towering over her.
She doesn't move away.
Quinn was too mean.
Sure, Noah would act like the football-slash-glee stud with a badass Mohawk and even badass-er (Rachel couldn't find a word, for once) guns (that's how he referred to them), but deep inside he was just an insecure, small-town boy who was overcompensating for his father's departure and the lack of testosterone in his house. His voice was strong and menacing when he swaggered down the halls but she couldn't forget how he softened his touch to her cheek as they made out on her bed—
"Rachel, are you alright?" Mr. Schuester asked. Finn was already at the other side of the room and she was supposed to be with him. She blushed and nodded mutely, glancing quickly at Puck who wore a familiar smirk on his face. "Take it from the second verse."
She noted the venom and disgust on Quinn's tone whenever they would interact with each other, and she noticed how tighter she would hold on to Finn whenever he would pass by and say hello (or open with an insult, which she now thinks of as blunt honesty). He was a masochist, a glutton for punishment. Quinn treated him horribly and yet she would still catch him glancing at her sometimes. He doesn't deserve that, no matter how much of a jerk he was. No one does.
"Puck, we need some accompaniment." Mr. Schuester instructed, and Puck took the guitar and strummed the melody softly. She loved how he looked whenever he was playing guitar. He looked so peaceful and so (pardon the word) damn hot—
"Rachel it's your line," Finn said softly, a look of concern etched on his face.
"I'm sorry, can we go over it again?" she asked, making sure to look at Finn this time. Finn was safe. Finn didn't have a prickly head, or a (too) piercing gaze, or a body which would make both of her dads squeal with—she sighed. Who was she kidding.
(she stole another glance just because.)
They finished the song and Finn showered her with smiles and compliments on her singing. She nodded graciously (quite distractedly, too) and walked over to Noah as Finn was about to launch into another 'your voice is so amazing' tirade.
"That was good," she said, smiling.
"I know," he replied, and, in barely a whisper, "thanks Rachel."