Extracting with a bottomless filter holder removes the coffee's journey through the spout resulting up to 50% more Crema. A fairly new method of extracting the positives are as follows-

Helps training and can indicate  correct tamping is being applied, also the correct grind.

Easier to clean.

More crema as mentioned.

Larger cup clearance height.

Larger deeper baskets if required.

Bottomless porta filters available for most manufacturers of espresso machines - Buy online Coffee Spares Direct.