Played a whole bunch of WT (mostly plane sim) and WoWs, had a lot of fun in both.
Both have an aspect of grind to them, but neither will actually give you an advantage in a single game for having done said grind (apart from some marginal 'crew' and equipment effects, the notable exception being in WT tanks where you have to unlock the ability to put out fires. That part is cancer.).
The grind is mainly to unlock 'more advanced' (higher performance) vehicles, but the battles for both are always somewhat balanced fairly tightly around a single performance level.
If you like looking at pretty WW2 vehicles both are fantastic. Just don't 'buy in' to the sunk cost fallacy of the grind and instead play for fun. I'd say just download them and have a go, both are free to play.
That said, DCS is also technically free to play if you fancy a higher fidelity plane sim and both it and the IL2 series have much better flight models than war thunder which can vary wildly in authenticity from plane to plane.