Does a larger lava pillar produce a lot more light?

It would make light travel a whopping one block further in the three directions you add the lava to.

Given the lava physics in Minecraft, light intensity and radius are the same. A candle gives 14 luminance and 14 radius. Lava and sunlight have 15 luminance instead.

Here's how light would spread if lava had 5 luminance:

     1
    121
   12321
  12GGG21
 123GLG321
  12GGG21
   12321
    121
     1

Here's the same with a 2×2 source:

     11
    1221
   123321
  12GGGG21
 123GLLG321
 123GLLG321
  12GGGG21
   123321
    1221
     11

...but that's a waste. Here's what the same amount of resources (4 lava sources, 12 glass columns) can get you:

     1     1   
    121   121  
   12321 12321 
  123G32123G321
 123GLG323GLG321
  123G32123G321
   12321212321   + 1 lava source
    121232121  
     123G321    (This is just an
    123GLG321    example, you can
     123G321     probably do
      12321      better than this.)
       121
        1   

Also be aware that light also spreads out vertically: a light source one square above ground level is what will give maximum luminance at ground level. Light any higher or any lower will give you less luminance, as light has to travel through more air to reach the ground.

Thus, the height of the pillar doesn't matter if all you care about is mobs not spawning.

Remember each level of the 16 levels of luminance (0-15) appears to 20% darker than the other.