Fill every time. More control.

Depends on what I'm trying to achieve.

Tend to think about it in terms of how I would code.

• Fill opacity maps to rgba in css.
• Whereas Layer opacity is just opacity.

Although sometimes, if I want a transparent box with only a border, then I'll set the background of the box to match the page background. Otherwise it's kinda difficult to click/select it.

Depends what you are doing. Checkout example

I'd like to be able to control the Fill property's alpha value with the same keystrokes as Layer Opacity, but add "Shift", much like how Photoshop handled it.

Depends on the use case, definitely not a universal decision. You listed all the pros and cons for both.

A little off-topic, but BC broke some handy features in the fill opacity controls in recent updates (be it by design or not).

You could go to the dropdown, select a color you wanted and press 1. By doing so you would change the fill opacity to 10%. Now the color value is preselected after choosing a color, so any typing replaces the color value. And now you'd have to press Tab 4 times, then enter the value you want (10%) and additionally Enter to submit the change. Which is kind of a lot of input (7 key presses to 1).

If I'm trying to put something out of my head using the numbers to toggle layer opacity is definitely my go to solution. If I'm preparing something to send engineers/other designers fill opacity is my go to solution.

Both! Like @alex-pate mentioned, I like to have the style scheme match the coding approach when possible. Also, like you mentioned, both have their pros, which I believe warrant having them.

Depends what I'm trying to do. If it's purely as a fill only layer, I'll use layer opacity so I can use the keyboard shortcuts. Otherwise, fill opacity.

It depends, preferably Fill Opacity, but sometimes Layer Opacity is enough.

The key here is that you can trigger Layer Opacity with shortcuts in Sketch (and as far as I remember in PS too) by hitting 0 to 9 for 10% increments.

Fill if I'm being precise and actually make a style.

I use Layer only when trying stuff out (especially on groups) because of the quick hot keys.

If its for the use case that you're showing here, I'll use the layer opacity.

However, I often use fill opacity to blend multiple fills together on the same shape.

Each has its own use.

I constantly use layer opacity with keyboard shortcuts because is fast in any escenario and I also use it with fonts (btw you can get specific opacity numbers like 37 or 68 using the keyboard)

If I need different opacity for a fill and a stroke then I use their own setting)

Updating your templates for sketch? Perfect! :]

For the same reason Eli mentioned: fill.

Fill. Much more control.

Why not both?