You only took into account 4 bows which have unique effects, while there aren´t any guns, except for the Candy Corn Rifle (Which has it´s own ammo) with an unique effect. In both cases, the effects usually come from the kind of bullet/arrow used, so you must count all of them.Well either way bows are far more lacking than guns because really? Wood bows and bows made of ores are barely worth mentioning leaving only four bows, Marrow, Ice Bow, Pulse Bow, and Tsunami. There is repeaters but I mean I feel like the
only one that stands out is the Chlorophyte Shotbow, and the Stake Launcher. So basically the bows may have quantity but pretty much no quality, and the guns has almost as much quantity and a lot of quality. It's not because the ones i'm mentioning are endgame it's just they're unique and not those boring old Gold Bows that nobody ever makes. I should not even have to be saying this everyone knows that bows are more lacking than guns.
There is also the fact that the only reason guns seem to all have really unique effects is because they often take some stats to their logical extremes (The Sniper Rifle and the Chain Gun, for starters), but they are either Shotguns (3 guns); 5 semi-automatic, fast guns; 5 fast, automatic guns (6 if the SDMG is counted, which it shouldn´t until it becomes obtainable), 3 slow-firing guns, 1 burst-firing gun.