Yes, sex is better with a bigger cock. There's probably a limit to that - there's such a thing as a cock being too big - but in general, it feels better if a guy has a bigger cock.
That's just the physical sensations, though. The in and out. The sense of fullness. The sense of being 'stretched' just a little. The sense of him reaching deeper inside you than your husband does. Those are all good things, but that's not the only way in which size matters. Let's talk about some of the other ways:
The First Touch - They're fooling around for the first time. Everyone is still fully clothed. She's kissing him. She's caressing him. Her hand makes its way between his legs. She rubs his cock through his jeans. She discovers he's big. She moans. Her pussy dampens. Now she's more excited about the night, about the sex she's about to have. Not a single article of clothing has come off and she's already worked up because he's got a big cock.
The Reveal - The more cocks a woman sees - in person, that is - the more attuned she is to the sense of excitement - and I'm talking sexual excitement - that happens when the cock is big. There's a little rush of pleasure. A tingling between our legs. Sometimes a smile creeps across our faces because we know there's a very good chance the sex is going to be good. In case you're wondering, there's absolutely a sense of disappointment when the dick is small. A gentle drying of the pussy. The knowledge that the sex isn't going to be as good as it could be.
The First Grip - Sometimes there's something truly hot about wrapping your fingers around a dick and finding that they don't connect. He's too thick to fully grasp him. There's something hot about being able to move your hand up and down a shaft, too, about there being plenty of room to play with him. It's rare, but there's something hot about being able to wrap both hands around a dick - and those hands being stacked, of course - and that's a rare treat. The dick isn't inside her yet, but she's all worked up because he's big, because he's long, because he's thick, and for a woman all the stuff that happens beforehand to get her hot can be just as important as the actual sex when it comes to giving her a mind-bending orgasm.
His Confidence - Men with big cocks tend to be more confident lovers. Yes, his size makes the sex feel better, but it might be equally important that he fucks with confidence. There's something irresistible about that. Something fantastically hot about it, in fact. It's hard to describe, of course, but a woman knows it when she feels it, and a big-dicked man is a lot more likely to be a confident lover.
The Joy of Satisfying Him - This one isn't always obvious. Sometimes it happens on a deep, subconscious level. But, the basic idea is that a confident, big-dicked man is more desirable. He's a rare find. Because of that, it can be a turn on to satisfy him. It can be a turn on to know that he wants you. It can be a massive turn on, in fact, to know that your pussy made him and his big cock feel so good that he wants to come back for more. It's not fair - it's not like it's your fault that you have a small dick - but sometimes it's just hotter to satisfy a man with a big cock.
Most of this is stuff that women don't really think about. Not consciously, at least. It does have an effect on the quality of the sex, though, so remember that size matters in more ways than you might imagine, cucks.