I am planning a (not explicitly optimised) Ranger/Monk character, that uses Druidic Warrior to cast Shillelagh:
Druidic Warrior
You learn two cantrips of your choice from the druid spell list. They count as ranger spells for you, and Wisdom is your spellcasting ability for them.
The spell in question:
The wood of a club or quarterstaff you are holding is imbued with nature's power. For the duration, you can use your spellcasting ability instead of Strength for the attack and damage rolls of melee attacks using that weapon, and the weapon's damage die becomes a d8. The weapon also becomes magical, if it isn't already. The spell ends if you cast it again or if you let go of the weapon.
However would it be unbalanced to ask a DM to allow it to transform into a sword as part of the spell (while retaining all other properties including the 1d8 damage)? The only thing I can think of us the damage type changes from bludgeoning the slashing.
Part of motivation is flavour: magical weapon cool; magical transforming weapon, way cooler.
The other part is that if I picked Kensei as my monk subclass, I could pick Longsword as my Kensei weapon, and have my Shillelagh count as that.
Best Answer
Is converting bludgeoning to slashing damage balanced? Yes, according to the Great Monster Spreadsheet!
Damage type generally only matters in the context of vulnerabilities, resistances, and immunities. For instance, force damage is much more powerful than poison damage, since so many monsters have resistance/immunity to poison, but almost none have any kind of advantage against force. If two damage types generally have the same amount of vulnerabilities, resistances, and immunities, then they're pretty much interchangeable except in special circumstances.
Reddit user u/RufflesDmAccount put together this spreadsheet of all the monsters in D&D 5e, including their damage sensitivities. Sifting through the data with some regular expressions, we find the following counts:
So bludgeoning is a slightly more powerful damage type than slashing, having a few more vulnerabilities and no specific immunities, but it's very slight. You won't lose any combat effectiveness unless you're fighting a horde of skeletons, and this is definitely a balanced change.