Bits are like Guns. Either will hurt you in the right hands. The bit is not the harsh part it is the riders hands. My young horses are started in a twisted snaffle. They move up as they get light and responsive. TO finally they are being ridden and showing in a high port bit.
The idea is not to be harsh or MAKE the horse work or correct anything. It is to make and keep the horse light and responsive. The less movement of your hands is needed to cue the horse. Now in the wrong hands these bits can be very very harsh. However if the right hands it can make a horse responsive to just a slight movement of your hand.
-- I ride 3/4 of my guys in bits. One in a single-joint snaffle, another in a single joint rubber snaffle, and one in (ahhh I forget!).
My personal pony, Prince, however, I will -NOT- ride in a bit. He has been broke for 7 years, being ridden regularly. Although, he was abused and was probably ridden in harsh bits. When I got him, he was ridden in the second bit listed in the original post. Not harsh at all, but I never rode in a bit (due to his teeth..) - so I rode in a simple nylon halter. He responded well. Two or so days ago, I rode him in his regular bit; and he bolted, bucked, and WOULD NOT PAY ATTENTION. I switched him to his halter, and he responded 3 times better!
It all does depend on the horse and rider.