Which sperms are stronger?

There are several types of sperm. Remember, these are broad categories. There exist many variations inside each type, and each person will probably have more than one type.
Speeders – aka, Swimmers, Jumpers, “The Blitz” etc.
These sperm have an over developed flagellum and an underdeveloped head. They succeed by arriving at eggs in high number before other sperm and then penetrating en masse. Each Speeder has only 2/5ths of the human genome, so obviously high numbers have to reach the egg. These sperm often cause twins or triplets, as well as some weird numbers in between (half-siblings, etc).
Castles – aka, Blockers, Walls, “Linebackers” etc.
These sperm have oversized heads and long, but weak, flagella. They carry a massive genetic payload – enough to impregnate four or five eggs. When left alone, a single Castle can impregnate a female for an indefinite period of time. But this rarely happens. Instead, a large number of Castles will “block” for other types of sperm by forming a plug at the opening. Castles and Speeders work well in combination.
Razors – aka, Scissors, Slicers, “Edwards” etc.
These sperm have normal sized flagella and a sufficient genetic load to fertilize an egg. Their trick is their spiny flagellum. A flock of Razors can shred sperm from competing males simply by swimming by. They also, sometimes, rupture defensive Castles. These sperm are very efficient, but there are draw backs. Fratricide is a major problem. They’re also not as fast as Speeders. And then there’s the risk of lacerating the egg beyond repair. This is where many birth defects originate.
Of course there are other kinds, Burrowers, Spies, Clowners, the “Sheep”, Slinkies, Sickles, Whooping Sperm, and the infamous Walken Strain. None of these are as significant as the Big Three, mainly because they’re adapted to very specific battlegrounds. In environments where obstacles such as condoms predominate, for example, the Burrowers are obviously at an advantage.
Again, most people have a combination of different types. Debates over which combos you should choose still rage in scientific circles. Popular archetypes in the current metawomb environment include the One-Two Punch (Castles blocking for Speeders); the variant, the One-Two Donkey Punch; and the Walken Surprise, which combines the offensive power of Razors and Burrowers with the X-Factor of the Walken Strain. Consult your doctor on which combo is right for you.