Have to agree, wasn’t impressed with the 750a, much prefer the GD, my ultimate would be the cross slot as it deals with chopped straw better. From my limited experience if I’d been younger I’d go with something like a Claydon for a few years then cross slot or GDTbh going from a plough based system to DD, I'd go with a tine, but it'd need to be able to cope with a cover crop.
The Atchison is probably the simplest and most capable.
I'd only look at a disc sometime down the line personally.
And then it'd be a gd, mates got a JD, it's good, but a lot less forgiving than the gd.
The gd always covers the seed, the JD often leaves an open slot.