Best way to change the property an object or gui?

Is there a "Best Method" to change the property of an object or GUI, like for example the transparency of a Frame in a GUI. There are two ways that I know of, I could either use a for-loop or TweenService to change the transparency. Is there another way that I am missing?

Does one cause more lag? Can one be more efficient? Does one look more appealing?

Here's a for-loop for the transparency of a block

local block = script.Parent

while true do
    for i = 1, 10 do
        block.Transparency = block.Transparency + 0.1
        wait(1)
    end
    wait(2)
    for i = 1, 10 do
        block.Transparency = block.Transparency - 0.1
        wait(1)
    end
    wait(2)
end

Here's the TweenService for the transparency of a block

local block = script.Parent
local ts = game:GetService("TweenService")
local tween = nil

function tweenObject(t)
    local info = TweenInfo.new(10)
    return ts:Create(block, info, {Transparency = t})
end

while true do
    tween = tweenObject(1)
    tween:Play()
    wait(12)
    tween = tweenObject(0)
    tween:Play()
    wait(12)
end

Which one is the better method to use? Or under some circumstances, which one should be used?