I have tried both and now I only use cubes
When feeding loose worms, as soon as I throw the food in water, fish ate them before they could soak in the water and I see bloated stomach and fish swimming uneasy. If I pre soak, the worms dont stay on top of the water line and a good amount of them get sucked in the filter.
When feeding cubes, I press them hard against the glass to get any air in the cube out. No more bloated stomach problem and like Al said, fish get comfortable eating off my hand and I love it. I dont lose any worm to my filter which is good for my fish and my pocket..