Short answer:
$FX staking will receive $FX via participation (automated and less work).
$PUNDIX staking will receive $FX via contribution (more work and uncertain).
Long answer:
f(x) Core is Function X Mainnet and the chain that connects all other chains, we can have hundreds of Function X chains and they will all be linked to each other via the brain and central nervous system f(x)Core. $FX token is the native token in f(x)Core and naturally new tokens in each new f(x)Core block will have $FX tokens. These new $FX tokens are rewarded to stakers who own $FX, such as you. This process is automated and smart contracted provided you delegate your tokens.
Important point. Most but not all newly created $FX are automatically allocated for $FX stakers. Some newly created tokens go to pools for developers, liquidity, community etc as stated in white paper and HashOuts Request-for-comments. Some $FX tokens in these pool will likely go to $PUNDIX tokens holders. Simply because there is alot Pundi X products can play in the ecosystem and Function X needs the utility that Pundi X products bring into the ecosystem. If f(x) Core is the brains and central nervous system, then Pundi X products will be the limbs. XPOS will run its own chain on Function X, and will have its own $PUNDIX staking, usage and reward mechanism, which I am very excited about. $FX will likely benefit from it too, hence a win-win.