Why use #show vs #showtootip in a macro?

#showtooltip shows the spell tooltip on mouseover and #show doesn't (I think).

It also updated based on whatever is the active spell for the macro. e.g. based on modifier key pressed etc.

Both #show and #showtooltip can take any spell name and [mod] options as parameters.

e.g - DK dps/tanking dual spec switch macro

#show [spec:1] Parry; [spec:2] Bone Shield 
/usetalents [spec:1] 2; [spec:2] 1

Because they perform different functionality.

Also, #show is only used when you use the ? icon, and is used to change the icon dynamically to which ever will be cast - or, if you're lazy like me, to prevent you needing to search out the correct icon from the list. Whereas #showtooltip will show the tooltip - should you have them turned on - of the spell that will be cast when you click the button/key.

There is nothing to prevent you from using both at the same time

One reason to use #show instead of #showtooltip is to tell apart multiple macros that use the same primary spell, but with different other details like targetting. If you just use #show, the tooltip will be the macro name, while if you use #showtooltip, the tooltips would be the spell info, which would be the same for both.

For example, let's say I have two macros for Power Infusion, one to cast it on myself and one to cast it on my mage friend.

The macros could be something like this:

Macro: PI myself
#show Power Infusion
/cast [target=player] Power Infusion

and

Macro: PI for DPS
#show Power Infusion
/target MagewithgreatDPS
/cast Power Infusion
/w MagewithgreatDPS I just cast Power Infusion on you!

Since I use #show, I can tell the buttons apart by their tooltips, which will say "PI myself" and "PI for DPS." If I had used #showtooltip, they would both just show the tooltip for Power Infusion, which is redundant, and really unnecessary since I know what PI does. And #show still shows me the spell cooldown and whether it is in range.

The only other reason I could see to use #show is if you would hit the 255 character limit with #showtooltip, though you'd have to be a very sophisticated macro writer for 7 characters to matter. :)

Found on WoWWiki.com's Macro API page

Metacommands pass data to the WoW client to affect its appearance on the action bar. Metacommands are preceded by a "#" symbol. Unknown metacommands will be silently ignored.

#show - Affects the button's icon on the Action Bar.

#showtooltip - tooltip - Affects the button's icon and tooltip on the Action Bar.

I personally find, however, that if I am creating two different macros for the same spell (one for my target, and one for myself), I prefer to choose two different icons, negating the need to use either #show or #showtooltip.

Also, if I remember correctly, you can choose to not include either, and just use the ? icon and obtain the same results you would get by using #show, ultimately reducing the number of characters used by 12, which could allow you to add additional functionality to the macro.