No. The LMG34 is not more useful.
The IR STG44s actually have more DPS than the LMG34 at max range as long as the enemy unit is in cover, because of their 0.9 cover accuracy multiplier.
The rare chance of grabbing a second LMG or if the enemy never uses cover are the only two scenarios in which the LMG34 upgrade is better.
I test with CCM and Range map
30m ,MG34 ober and IR ober shot each other
only in heavy cover,IR ober can give MG34 ober almost same damange
Final score, MG34:IR 4:2,and IR ober almost die,in one test,MG34 ober only lost half HP but didn't lost man