Native staking
Your SOL sits in a stake account delegated to a validator, and rewards are paid into that account at the end of each epoch. To exit you deactivate the account, which takes effect at the next epoch boundary, and then withdraw. Sources describe the wait as roughly one to three days. A new stake account takes one to two epochs to become active.
Liquid staking
You send SOL to a stake pool and receive a liquid staking token that represents your share of the pool. Rewards compound into the pool each epoch, so the token rises in value against SOL. To exit quickly you swap the token for SOL on a DEX, and you pay the route's fees, spread and price impact. Marinade also offers a delayed unstake of about one epoch. Liquidity can run thin if pools become depleted.
Instant unstake for native stake
Some services take over your native stake and send SOL back at once. Marinade's docs say this needs a stake account of at least 1 SOL that has been active for at least two epochs.
Fees
Fees vary by provider. Marinade's docs list no deposit fee on staking, no protocol fee on instant unstake, and a 0.2% protocol fee on delayed unstake. See Marinade and Sanctum.
Choosing
Native staking keeps your SOL in a stake account with predictable exit timing. Liquid staking adds a tradable token and faster exits, in return for pool fees, smart-contract risk and the chance of selling at a discount.