What scale should we game in?

I have been in various discussions regarding historical wargaming miniature scales and why gamers choose certain scales.  We should choose the scale we want to.  We all have our reasons for picking a certain scale whether it is for land, air, or naval battles.  I've ended up with all sorts of scale miniatures.

Here are my reasons for picking my scales in order of decision making:

1. I have a battle in mind that I want to wargame.  Do I have some of the miniatures in a scale already?
2. What rules will I use?  Sometimes rules are designed to use a range of scales.
3. Is there a company which supplies all the needed miniatures for the battle.  If only one company has the needed miniatures, then I am stuck with that scale.  If this scale results in too many miniatures to paint or too few, then I probably will not do the battle (examples: Jutland or Gettysburg).
4. What is the size of the battle?  To cover the whole battle maybe painting up 6mm or 15mm will work.  If it is a small battle, maybe 28mm as a skirmish battle will work.  28mm could also work for a big battle, but do a portion of the main battle.
5. Based on the figure count, will it cost too much or result in me painting for years?  If so, then don't move forward with this possible project.

This is my current scale variety in my collection:

Naval

• 1:600 - ACW
• 1:1000 - Russo-Japanese War
• 1:1200 - Age of Sail (2 ships), War of the Triple Alliance
• 1:2400 - WWI, WWII

Air

• 1:144 - WWII, Korean War, Vietnam
• 1:600 - WWII
• 1:1200 - WWII
• 1:2400 - WWII

Land

• 28mm - War of 1812, Philippine-American War, Rebellions of 1837-1838
• 25mm - Aztec-Conquistador
• 15mm - Boer War, Crimean War, Battle of Flodden, War of 1812, Italian War of 1859
• 10/12mm - Vietnam, WWI, WWII, Korean War
• 3mm - Guns for War of the Triple Alliance (1 stand)

I have others unpainted periods that will expand this list.  In the future I can see myself adding 6mm.

I used to have 1:72 / 20mm WWII which I used with Rapid Fire, but decided to bail on that for something smaller (10mm) with Blitzkrieg Commander ruleset.  I found it looked better for the battles I wanted to do.  Also, so much easier to store these miniatures.

What scales would I recommend staying clear of? I think scales smaller than 6mm (land) and smaller than 1:1200 (air).  Naval wise, I think all the scales are fine.  My struggle is when the ship models get large and lack the maneuver room on the table (i.e. 1:1000 Russo-Japanese capital ships).  I guess I struggle getting excited about miniatures I can't tell what they are.