I feel that the answer to the question would depend on the situation, but, I am hoping that someone can provide me (and others who may look at this question) a good explanation into efficient scripting.
Also, to clarify what I mean by "efficient", I mean it in many ways, but the primary standards being: -Hogging less resources -Runs faster with the least amount of function calls I mean, if I make stuff on the Explorer, it seems like I am putting in less lines of code, but because functions here are sometimes covered with syntactic sugar (and plus, I don't know how efficiently ROBLOX instantiates something already put into say, game.ReplicatedStorage), I really don't have a solid clue which one would be more efficient.
Here are two situations:
Would doing this in a Script...
local event = Instance.new("RemoteEvent", game.ReplicatedStorage)
...be more efficient than putting a RemoteEvent in ReplicatedStorage through the Explorer in Roblox Studio so that instead I can do...
local event = game.ReplicatedStorage.RemoteEvent
Or for instance, in a gun tool, would it be more efficient to instantiate a bullet in the script like...
local bullet= Instance.new('Part') do
bullet.Name = 'Rocket'
bullet.FormFactor = Enum.FormFactor.Custom
bullet.Size = ROCKET_PART_SIZE
bullet.CanCollide = false
...or put in a bullet in the tool (or some other location) through the Explorer in Roblox Studio and make the local variable bullet reference like...
local bullet= script.Parent.bullet

4 comments
Why on earth would one be more "efficient" than the other? Efficient in what way?
My question: local bullet = Instance.new('Part') do -- Makes no sense to put 'do'.
"local bullet = Instance.new('Part') do" is actually from UristMcSparks' rocket tool available from Free Models. And, knowing his scripting capabilities, I have no doubt that he had something in mind...
@BlueTaslem, I'm sorry I wasn't very clear. I read my post again, and yes, it was a bit unclear. I edited it to explain what I meant by "efficient".