DPS ranges 10/20/35
Penal squad vet 3
41.3/33.6/20.6
LMG Grenadier squad vet 3
23.9/27.1/23.7
ST44 VG sqaud vet 3
33.2/24.4/11.7
1bar vet3 Rifleman have 37,4/24/15 dmg at range 10/20/35.
2bar vet3 Rifleman have 41,4/28,3/18,21 dmg at range 10/20/35.
(number provided by Geblobt)
Note that Penal have superior DPS that double bar riflemen at ranges above 10.
As for people who claim that some others unit should also be included, I advice them to the provide the stat themselves instead of coming up with conspiracy theories.
Taking your numbers Riflemen seems to be closest. So I tested Vet 3 Rifles with double Bar in green cover versus Vet3 Penals in green cover at mid range in vanilla version of the game (since this stats are taken out of vanilla).
3 of 4 times the Rifles won. Why is that so inspite of Penals having more damage output and beeing one man more + having the ability "To the last man"?
Easy, you just can't compare damge values only. Rifles for example have much higher received acc at Vet3. This means they drop their first soldier later. In addition a lot of the firepower of the Rifles is concentrated in the last two individuals of their squads with the Bars. So the damage of the penals drops faster by loosing men. This is the same versus any unit with an upgraded weapon. "To the last man" seems to not compensate fully for that.
Since Penals lack a lot of utility in comparison to other infantry squads (Rifles for example with nades and AT nades and some interesting doctrinal stuff), they should at least scale better into lategame.
Another interesting option would be to plant them at Vet0 and only lock the PTRS rifle upgrade behind T1. Make them a little bit cheaper and lock 6th man behind T1 too. That way you wouldn't loose map control totally if going for Penals instead of Conscripts early on.