Swap.Coffee is a DEX aggregator that selects the best offer among several DEXs to provide the best rate. And for large swaps, the swap can be split into multiple swaps with multiple DEXes at once to increase stability. STON.fi in turn is the largest DEX on the #TON blockchain, actively developing solutions to improve the quality of the platform and Cross-Chain.

1. Swaps
It would seem that DEX aggregators should provide a better exchange rate than DEXes, but there are caveats here as well.
For example, when swapping $1M $NOT to $USDT on Swap.Coffee, a user will get $7653, while on STON.fi only $7641. But when swapping a smaller amount, for example 10000 $HMSTR to $TON the results will be similar: 5.44 TON on STON.fi and 5.4 TON on Swap.Coffee. But, you have to spend 0.4 TON for a swap on Swap.Coffee and only 0.2 on STON.fi. Thus, DEX aggregator shows itself better at swaps for larger amounts, and STON.fi - for smaller amounts.
By the way, STON.fi is developing the #Omniston protocol, which also chooses the best rate among liquidity aggregators, but it also provides zero slippage.

2. Interface
Both products are oriented to end users, so it is quite appropriate to compare their interfaces. Swap.Coffee has a sharper and more aggressive interface, and additional functions are not obviously located. STON.fi is the opposite: the interface is made in soft colors, which is a plus for me personally.

3. DEX vs DEX aggregator
The main function of both products is the same - swap. But the ways to achieve it are different: Aggregators take liquidity from different sources, and DEX are those sources. This is the main functional difference - liquidity pools. They are available only on DEX and provide quite high APRs for liquidity providers. Also, some liquidity pools participate in farming, providing even higher APRs. For example, for the $MAJOR/TON pair the APR is 72% and for the $DOGS/$X pair it is 66%.