Horse bit questions

disclaimer: my horse is NOT currently being ridden in any of the bits listed below. He is in a KK French link loose ring bit.

http://www.doversaddlery.com/gina-miles-waterford-loose-rng/p/X1-01699/#ProductTabs

http://www.doversaddlery.com/jp-ported-hunter-dee/p/X1-01638/

But, in the past, other trainers (not while I was riding him - he was leased out) have ridden my horse in the following two bits. My question, why? What do these bits do/what is their purpose?

I know before I bought my horse he supposedly had a habit of trying to get his tongue over the bit. I haven’t experienced that problem since he came back from a lease.

I’m just curious and want to know more. I’ve only used soft/gentle bits on all the horses I’ve ridden and never really had to mess with a “stronger bit”.

The snaffle doesn’t look harsh or strong. Just has more room for their tongue similar to the myler comfort snaffle.

The Waterford is also not harsh. It is often used for horses that lock their jaw and are inclined to pull. The multiple joint leave make it so there isn’t a fixed point on the bit to lean on. Also no nut cracker action like that of a single joint snaffle.

Neither bit is legal for dressage but fine for jumping.