My, this is going to be an epic..like "War and Peace', or Proust 'Remembrance of things passed"

...but my initial observation was based on the glaring difference between the 47deg. glacis of Fireflies Nos.'2'. '13'. and '4' and the
60deg. glacis of the 2 bog standard Shermans. Clearly, the massive 17-pounder

,the welded on extras, and the picnic box (radio) grafted onto the rear of the turret, are also stand out features...
From what I've read (and it's not a lot...on the Sherman, anyway), Fireflies were only based on the original M4 with fully welded hull, and this mutated into the Sherman 1c Firefly. Equally numerous were the M4A4s..with extended stern. These morphed into the Sherman Firefly Vc, and then the Sherman Hybrid M4 (Composite) partly cast/partly welded also became the Sherman 1c. No other versions were used, but apparently this has been disputed. Apart from detail changes to hatches, MG post, and other cosmetic facelift scars, etc., the Sherman Firefly was still a Sherman toaster, with a massive British anti-tank gun fitted..'toaster', or roaster, that is, until water jacketing was used for ammo to reduce in-house incineration..
Personally, I'm not keen on the Sherman. It had a high centre of gravity, affecting stability, and a high profile relative to overall size in the Landscape (like its predecessor, the M3 Lee), making aiming an almost leisurely pursuit for german 88s, whether from an anti-tank position, or from tiger turret. I can already hear the howls of protest

and rage

from Sherman fans...but it's also a fairly ugly tank! Pity the War office couldn't get more Comets out there earlier!
However, since my Dad and my Uncle were both in armoured units during the war, they would have been familiar with the Firefly...and the bog standard Sherman. If I had a model, though, it would have to be the to Vc Firefly to reflect their experience
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.