Pistols generally provide modest boosts to DPS and tend to have few or no penalties, though the benefits they provide are often smaller than with other weapons. The heroes that use Pistols tend to be weak-to-average combatants and are often operators.
SMGs provide large increases in damage, cooldown, and range, but also have noticeable penalties to speed. SMG users tend to be slow but can deal and often take heavy damage, and they also have the longest attack range. There are less SMGs than any other weapon type, making them comparatively rarer to find.
Spears increase damage but can also boost a variety of additional stats depending on the specific weapon. Many increase speed or attack range, useful for the several speedy spear users. Spear users vary across the board, though many are tanky and/or deal potent damage.
Swords potently increase their user's damage through attack power or cooldown, but the specifics vary widely between different weapons. Many boost the defense or HP of the user unlike other weapon types. Sword users vary widely in their roles and have no major common strength. There are more swords than any other weapon, making them a bit more common to find - though there are more 'weak' examples in this weapon type than any other type as well.