Auto Finance Autopools and yield aggregators such as Yearn solve the same problem — a depositor wants a good rate on an asset without managing positions — and both hand back an ERC-4626 vault share for doing it. They differ in what the vault is allowed to hold and in how the decision to move capital gets made.
A yield aggregator vault is usually organized around strategies: discrete pieces of code, each implementing one way of earning on the deposited asset, with capital allocated between them. Adding a new venue generally means writing and deploying a new strategy, and the allocation between strategies is typically governed by the protocol's operators or by a defined allocator.
An Auto Finance Autopool is organized around destinations: a permitted set of specific liquidity pools and lending markets, all denominated in the Autopool's base asset. The rebalancing logic compares the destinations in that set continuously and moves capital when the yield differential is worth the gas and slippage cost of moving, rather than on an operator's schedule. What is being optimized is the allocation across venues, and it happens on-chain as part of the protocol rather than as an off-chain decision applied to it.
For a depositor the practical differences are narrower than the architectural ones. Both give an ERC-20 receipt token that appreciates as the underlying earns, both compound without manual claiming, and both are non-custodial and withdrawable subject to on-chain liquidity. Auto Finance Autopools currently charge no management or performance fee, where aggregator vaults commonly charge one or both. Fee terms change, so compare the current terms of any specific vault rather than relying on a general statement.
The honest summary: if the question is whether to hold a vault share or manage positions by hand, Autopools and aggregators are on the same side of it. If the question is which vault, the thing to compare is the permitted venue set, who decides the allocation within it, how often that decision is revisited, and what the vault charges.