Ive the Halfords 3 tonne ractchet ones, been very happy 
And me, far easier to use than the pin ones which are more fidely, just place the ratchet stand under the car and lift the sadle, the ratchet wil catch and let go of the sadle, one hand job.
Pin ones are 2 hand job which means you have to get both arms under the car and hence head and shoulders also to get the pin in while the car is only supported by the jack. Also and the chain brakes and the pin gets lost.
Ratchet ones seem to be lower than pin ones i think. Or is it because i have a better jack now. The lower the stands first setting means less jacking needed, handy if you have a smaller jack.
Ratchet stands all day long for me.
If anyone saw my old 2ton jack at the Ashridge meet they would see why 2.5 ton jack is a minimum imho esp if you have a soft drive, smaller wheels dig in and the jack twists and bends. I now have a 3ton jack and is bullet proof it seems, only down side is its bloody heavy. To heavy for the boot of the car and my back. Wanted 2.5 clark job but couldnt get one locally in time so 3 ton it is.