It's accuracy is the same as the Ostheer mortar ht I believe, it just has a lower rate of fire.
The ROF is almost the same between the two because the Ostheer mortar HT has a longer cooldown but no reload while the USF mortar HT has a longer reload but shorter cooldown.
The scatter on the USF HT is much, much lower (meaning it's more accurate)
The damage and AoE profiles are the same, I think the difference is the scatter on the USF mortar HT's barrage is higher (by a tiny bit) than the Ost Mortar HT's barrage.