Blood penis
From a medical perspective, guys' bits are divided into two types, the blood penis and the flesh penis. When it comes to getting turned on, both guys and girls experience a bit of swelling down there. But for blokes, it's way more obvious with a proper erection. This stiffening of the old chap is crucial for getting it on. But not every fella's member swells up the same way when they're aroused. Beyond individual size differences, there are these two types of todgers.
The typical flesh penis, or 'shower', is already pretty sizeable when it's soft and doesn't grow much when excited. So, when it gets hard, it stiffens up but doesn’t change size too much. As a rough guide, if the difference between soft and hard is less than four centimetres, it's likely a flesh penis. About 21% of European guys and 26% of American guys are 'showers'. They might have had an evolutionary edge in hotter places, being more eye-catching and appealing to the ladies.
On the flip side, 79% of German blokes have a blood penis. This type grows quite a bit when aroused - at least four centimetres more. Because it grows a lot when they're pleased, it's also called a 'grower'. A fully excited blood penis can double in size. Evolution-wise, these were probably handy in colder areas, shrinking in low temps and staying protected in the chilly old days without heating.
Whether a guy has a blood or flesh penis is all down to Mother Nature, or more specifically, his genes. Even before he's born, it's set in stone what kind of member he'll have. This comes down to the muscle cells and a membrane that make up the member, and the basic muscle tension in the soft state decides the type. As for which is better for getting it on, well, that's a bit tricky to say. Both types have their perks. And whether it's a blood penis or a flesh penis, it doesn't affect how hard it gets or a guy's staying power. Some ladies like the surprise factor during the deed, which they'll more likely get with 'growers'. Others prefer knowing upfront what size they're dealing with.