High Imperial Roman army vs Late Roman army

[Frank]

I would not look that much to the weapons. Both were pretty much capable to hack the others into pieces. The composition of the armies would be very different:

Let's assume a typical composition of 25.000 men. The Imperial Augustean Army has perhaps
- more heavy infantry (12000 vs. 8000)
- perhaps roughly equal amount of light infantry (8.000 vs. 7000)
- less archers (1000 vs. 3000)
- less field artillery (0 vs. 1000)
- more light cavalry (4000 vs. 2000)
- less mounted archers (0 vs. 3000)
- less heavy cavalry (0 vs 1000)

Honestly, I have no clue, who would win. These armies are just too different beasts. It is all about tactics and the generals. Remember Pompeius superior army against Julius Caesar!

One question is, will the imperial heavy infantry killing machine break the late roman lines, before the late roman cavalry can rout the imperial cavalry? Or will this imperial commander come up with a genious plan, rout the mounted archers and make the cataphracts easy targets for the light cavalry? Or will the lanciarii and archers of the late roman army stop the infantry charge of the imperials with waves of arrows, javelins, and ballista bolts before they even come into pilum-range? Or, ... and don't forget the weather, the gods and what they had for breakfast.

The imperial commander would perhaps say: "Holy shit, this looks like the Parthians have invented a decent infantry!"
The late roman commander: "God help us: Well organized West-Germans with good standardized armor and weapons should not exist!"

For both guys, this must be the strangest and most frightening sight ever.