When to use functions and when to decide that it is not worth it?

Recently, I had a discussion in the discord about whether or not to use :UpdateAsync or :SetAsync mainly because I did not need to access the previous values when saving the player's data. I have been mostly encouraged to use :UpdateAsync because it does not return a cached value. However, I don't need to know what the returned value is. Is it worth it to use :UpdateAsync which requires the creation of a function? Another thing that came up during that discussion was that I was creating two functions and using each only once. I am wondering when I should decide not to use functions and when to use functions. You see, I was setting an index in a table to the value returned by the functions and I felt that a function was easier. Here is the script:

local function saveData(player, retryCompatible)
	local dataStoreService = game:GetService("DataStoreService")
	local mainDataStore = dataStoreService:GetDataStore("generic")
	local function createTableOfNames(objectList)
		local newTable = {}
		for i,v in pairs(objectList:GetChildren()) do
			table.insert(newTable, v.Name)
		end
		return newTable
	end
	local function findEquipedTool(starterGear)
		local starterGearList = starterGear:GetChildren()
		if #starterGearList > 1 then
			return false
		else
			for i,v in pairs(starterGear:GetChildren()) do
				return v.Name
			end
		end
	end
	local replicatedStorage = game:GetSErvice("ReplicatedStorage")
	local stats = replicatedStorage.Stats
	local playerData = stats:FindFirstChild(player.Name)
	local purchasedItems = playerData.PurchasedItems
	local spaceCoins = playerData.SpaceCoins
	local snow = playerData.Snow
	local starterStuff = player.StarterGear
	local equippedTool = findEquipedTool(starterStuff)
	local listToSave = {}
	local specialKey = "User-"..player.UserId
	listToSave["Equipped"] = equippedTool
	listToSave[purchasedItems.Name] = createTableOfNames(purchasedItems:GetChildren())
	listToSave[spaceCoins.Name] = spaceCoins.Value
	listToSave[snow.Name] = snow.Value
	local success, message = pcall(
		mainDataStore.SetAsync,
		specialKey,
		listToSave
	)
	if not success and retryCompatible then
		local maxRetryAttempts = 3
		local retryAttempts = 0
		repeat
			wait(5)
			local success, message = pcall(
				mainDataStore.SetAsync,
				mainDataStore,
				specialKey, 
				listToSave
			)
			retryAttempts = retryAttempts + 1
		until retryAttempts == maxRetryAttempts or success
	end
end
return saveData

I am wondering if I should use :UpdateAsync in the areas where :SetAsync is being used. Also, you can see the two functions I create that I only use once each. I would appreciate any insight you guys may have. Thanks!

I don't know, but you can make a table save itself by using any of them even if you mix them in your script.