What is The best scaling mode for mobile ?

what"s the best scalling mode for mobile android and ios  to keep the charm of the game (dimension of the actor , the position ,  And keeping the game  centred  ....ect ?
Propose your techniques and your ideas for me
thnx

The "best" really depends on what your preferences are, but here's what I currently use:
Game resolution: 480x320
Graphics designed and imported at 4x
Scene size: 640x480 or higher
Camera either centered in scene or following an actor
Scaling mode: scale to fit (full screen)
Position certain actors like UI buttons based on the camera rather than the scene

The "best" really depends on what your preferences are, but here's what I currently use:
Game resolution: 480x320
Graphics designed and imported at 4x
Scene size: 640x480 or higher
Camera either centered in scene or following an actor
Scaling mode: scale to fit (full screen)
Position certain actors like UI buttons based on the camera rather than the scene

I do about the same.. I anchor the buttons to screen where I place them in level editor in stencyl... usually top left of the screen... @rob1221 what do you mean by based on camera? For the UI?

If I wanted an actor to always appear on the bottom of the screen, I would need to set the y position to the y of the camera + the screen height - the height of the button.  If anchoring, I think the camera y can be skipped.  It can't be set in the scene designer because the camera size varies based on device when using scale to fit (full screen).

Ahh! Ok!  I'll switch mine around.. I wondered why sometimes the button would be an inch away from the edge of screen.. but on flash it'll be fine.. 

Why are we still using 480 x 320? Nobody has that screen size anymore... Why not iPhone 4 resolution, 960 x 640?

It scales to fit.  I think it's more an aspect ratio... my live wallpapers i made in Eclipse are 480 by 800.. they work and look good on tablets and phones of all sizes.. they scale as well..., not sure why I chose that size... was years ago... I was using AndEngine, maybe they suggested it

Why are we still using 480 x 320? Nobody has that screen size anymore... Why not iPhone 4 resolution, 960 x 640?

960x640 may seem better at first, but it's actually worse overall (even for iOS exclusive), and here's why:
iPhone 4/5/6/7: 480x320 = 2x and 960x640 = 1x [winner = tie]
iPhone 6/7 Plus: 480x320 = 3x and 960x640 = 1x [winner = 480x320]
All iPads: 480x320 = 4x and 960x640 = 2x [winner = tie]

P.S. My current Android phone still has a resolution of 480x320.

Why are we still using 480 x 320? Nobody has that screen size anymore... Why not iPhone 4 resolution, 960 x 640?

960x640 may seem better at first, but it's actually worse overall (even for iOS exclusive), and here's why:
iPhone 4/5/6/7: 480x320 = 2x and 960x640 = 1x [winner = tie]
iPhone 6/7 Plus: 480x320 = 3x and 960x640 = 1x [winner = 480x320]
All iPads: 480x320 = 4x and 960x640 = 2x [winner = tie]

P.S. My current Android phone still has a resolution of 480x320.

I think this explanation should be added on the "Create a New Game..." page under Screen Size, where it recommends using 320x480 for mobile games. Maybe as  a "Why?" hyperlink-style tooltip.

Food for someone's thought.