You do not get lights to fight each other, Stuart is the only light tank somewhat designed to fight armor, two others are almost exclusively AI with added benefit of being able to dmg light armor.
You get them to fight infantry and light armor, this is what Luchs does incomparably better.
Also, luchs HP alone makes it best light tank by default by MILES.
Comparing light tanks in a direct combat makes as much sense as comparing mortars in direct combat-they do fight sometimes, but just because soviet one can precision strike german one it does not make it better then german one even in the slightest.
Except being able to one shot a squad is very powerful, the precision strikes are more likely to wipe squads than normal barrages.
Please, do me a favour and plug out keyboard.
I already proved that SP will win agasint AE at any range.
Why does this even matter? Sturms cost 40 more MP and are more expensive to reinforce.
Volks are far cheaper to reinforce, OKW barely needs munitions for other things and Volks are a 5 man squad instead of 4. They also get vet up to gain a lot of survivability and don't lose all their anti-infantry power after being upgraded.
OKW is very munitions starved early game, every grenade you use delays your Shreks heavily, which can be a killer.
T70 will win 1v1 with Luch, has great Recon mode but it's nowhere near to Luchs in terms of killing infantry. Luchs can melt infantry better than any other vehicle in game.
The T70 is more likely to one shot enemy squads and kill multiple models in each shot, while the Luchs does way more DPS.
Ultimately the T70 does well in it's roll, it could use some more health but other than that it can be excellent for killing stuff like Obers.