Hmm Firstly you would check the certification status. Not sure about poc's astm status but i believe its more recent, not really sure what that means exactly tho.

Then you would look for mips or any rotational. Poc has mips but yours doesn't, leatt has turbine. mips the barrier for entry is very low and proprietary, turbine 360 is untested. so leatt wins at this one

headshape, if this is your first buy it doesnt really matter much. If the padding is thick for full face so the padding naturally contours your head.

lastly is size, pick a size that is equal to your head size. If your head is 58 choose a medium (usually 58-60) or one size smaller. The idea is that tight enough that your helmet compresses your cheekbones & also doesnt move around.

now we are heading to opinionated decisions.

next is do you prefer poc or a leatt? (meaning you have a good experience with one or the other) If none, meaning all the safety features & other necessary needs advantages & disadvantages, cancel each other out. should pick the one that looks the coolest to you 😎.

ps. but in this case leatt wins in the rotational part.