I've never had a bow that was as quiet when shot three under as it was if it was shot with split fingers. Tuning helps, and the bows always shot fine and accurately, but always a bit louder three under.
I should add that most of my bows were bought used and as far as I know none of them are tillered specifically for shooting three under. I would assume that would help with noise.
Personally I hate a noisy bow so I still shoot split. If I tie small thread nock points, I can actually have a bow set up so that I can go back and forth between split finger and three under. Aside from the aiming or impact differences, the main thing I notice is the noise and feel between three under and split. Three under is loud and leaves plenty of vibration in the bow and limbs, split is much quieter and leaves very little vibration in the bow and limbs. At least that's how it works for me. I can see the accuracy potential of shooting three under, just can't stand the noise and feel of the bow.