First off, this is going to sound like(or be) a huge rant, but I don't really intend people to understand or agree or do anything, you can make what you want of it.
I hate beserkers that use Katanas. I match up the Chainsaw and the Katana in every aspect for the Beserker and reach the same conclusion; the chainsaw is better.
1) The sole, one advantage that the Katana has is it's running speed, though that in itself isn't much of an advantage. Sure the Chainsaw slows you down, but that's what the Beserker has a speed increase for, right?
2) The Katana's primary attack speed is fast, decent power, good for small specimens. The Chainsaw's primary attack speed is at around mach 10, and though each hit does less damage, the damage per second is far higher and better for smaller specimens. The Katana's Secondary attack is about the same speed as, if not slower than, the Chainsaw's secondary attack. In fact, I'd say the Chainsaw's secondary is around about the speed of the Katana's primary. Anyway, point being, the Chainsaw attacks and hits faster.
3) People argue that the Katana is roughly the same power, if only a tiny bit worse than the Chainsaw. Fair enough, if you're not a beserker, because due to the damage increase being a percentage, the higher your beserker level goes, the bigger this difference in damage becomes. Think about it; if Katana's stock power was 9 and Chainsaw's was 10(example values only) and there was a 50% increase in damage, Katana would end up at around 14(rounded up by 0.5, too) and the Chainsaw would be at 15(not rounded at all). Now when you bump it up to the level 5's 100% damage increase, Katana sits at 18 and the Chainsaw at 20. The difference increases, making the Chainsaw more powerful at level 5 than the Katana. Simple mathematics.
4) While a valid argument, this last argument hits me as being incredibly lame; "Katana only weighs 3 spaces." And? Why would you trade a powerful weapon, for a slightly less powerful weapon that allows you to hold one extra, near-useless weapon with no perk benefits added. You can already hold 9mm, handcannons, lever-action rifle, bullpup or an AK alongside the Chainsaw.....given the chance, would you rather have two of these weapons to attack crawlers and sirens with at a cost to your primary weapon's effectiveness, instead of only one? I know I wouldn't. Less weight isn't an advantage, only the running speed.
So yeah, I hate beserkers that use Katanas, since they're better suited to the Chainsaw. However the katana is a prime tool to be used by another perk, where space does indeed need to be saved for a more useful, perk benefitting, primary weapon. And I know some Ninja-loving Katana fans may want to remove my head for dissing their Katana-wielding beserker antics, but the way I see it, they should be thanking me for presenting many reasons why the Katana might not need nerfed at all; people just need to see that holding those extra weapons, while sacrificing their main source of strength, isn't much of an improvement for a Beserker.