OK, this is all bit of a diversion, but it has been keeping me thinking.
The 1877 British Field manual specifies that a Battalion in attack would have a frontage of 400 paces - call it 320 yards. This assumes 2 of the 8 companies in extended line, skirmishing forward, supported by 2 more in line formation 100 yards to their rear. The other 4 companies (the main body) will be in company columns 250 yards behind that. As the enemy is contacted, the support line will feed into and reinforce the firing line, and the main body hold itself in readiness to support the attack (frontally or by moving against the enemy's flank) or to cover a withdrawal.
The way this is normally represented on a gaming table is by a single battalion unit in a line, maybe 6" wide (if using 25/28mm and representing, say, 150 yards), and one rank deep. That's only half the frontage of a British formation in the 1870's. Or you can put the entire unit into skirmish, in which case it becomes very brittle if threatened as it has nothing to fall back on. But whichever way you do it, it looks like a "thin red streak tipped with a line of steel" rather than a box about as deep as it's wide, incorporating supports and reserves as it did.
To represent actual battlefields and tactics on a table will always demand a certain suspension of disbelief, but unsupported thin lines is a suspension too far for me. By using 4 "company" units, deployed two up and two back, I think it will look better, and make a battalion self-supporting to some extent.
So I'll go with company scale representation for my DoB2.
Another reason for using company scale is a sense of verisimilitude. I can't see divisions of troops being shipped out from Earth - it's too far, it's too expensive, and it denudes the homeland of available troops. Getting three British divisions into Egypt in 1882 was tough enough. Shipping a similar force half way across the solar system with very limited transport - and keeping it supplied there - just beggars the imagination. SC has a division (8 battalions) of British infantry plus a cavalry brigade and supporting troops on Mars, but it just feels too heavy. For me. YMMV - your Mars may vary.
I'm happy that going for company scale will allow me to field more units without having too many battalions Mars-side. They'll just have to recruit lots of local askaris/sepoys/whatever-the-martian-term-is, especially for the mounted arm.