Been playing Ost and I have to say I think right now the Grenadiers work the best as a "mainline" infantry. They cost very little and require no side techs and no vet for abilities. Volksgrenadiers used to be the best but after this last patch it seems like Grens have taken the mantle.
I don't consider Riflemen all that good because they are the least cost-efficient infantry unit in the game. Too expensive for their initial cost, too expenisve and time consuming for weapon rack upgrades, snare locked behind vet which isn't a quick process for them to vet up. They're really not that good when you factor in these extremely high costs. Most USF units have a very high cost but I think Riflemen have among the highest cost-benefit radio of any unit.
Tommies used to be the best Allied mainline infantry but the balance team took care of that last patch.
Consripts are probably the best Allied mainline right now with that 7th man upgrade. Takes a while to get there but once they do they are a pretty tough late game unit.
Grenadiers have a snare and great dps, which makes them ok at clearing AT guns late game, but have a hard time capping late game as they suffer from low model count. No moving DPS also makes it hard to support panther dives using them.
Infantry sections are really expensive to buy but incredibly durable. The ability to be at full health 100% of the time thanks to medkits, the ability to build sandbags and a low reinforcement cost, esp. comparatively to price with bolster, is super good and makes them tough as nails, but they have a hard time killing team weapons, especially AT guns, to support tanks
Penals are very powerful all ‘rounders, but are expensive and lack snares. To The Last Man means their DPS doesn’t drop as much as they lose models, making up for a lack of weapon upgrades, and satchels are great for clearing team weapons. Suffer from lack of snares and long range heavy AT in their tech path. Decent late capping power with high model count, but also high reinforcement cost.
Conscripts are great attrition troops late game with reserves, and good at clearing team weapons early thanks to oorah and Molotov, and have snares. Great for capping late game with high model count
Riflemen are great all rounders, good initial cost, reinforcement cost, snare, and weapon upgrades. Suffer from a lack of healing early game due to ambulance costing fuel, and being forced to close on grenadiers/ volks late game. High near dps and moving damage make them good for clearing team weapons.
Volksgrenadiers are quick to build, numerous and cheap, with snares, a good upgrade, and incendiary nades to deny cover early. Fall off late game due to poor trading and cover being created/destroyed. Good to cap with 5 models and low reinforcement cost, and good at killing AT guns with moving dps, good close dps and incendiary grenades