Tale of two pickups - rumble and bounce

[LittleGreyCat]

I've test driven two HiLux at the same main dealer.

One is June 2013, the other is October 2014. Both around 40,000 miles.

The slightly older one drives very differently. There is a judder like wheel (or drive shaft) balance at around 70 mph on dual carriageway, and the vehicle is much more bouncy at all speeds, but still noticeable at 30-40 mph around town. Very bouncy on a country lane.

The other is like a completely different range of vehicle, without the rumble or the bounce.

The rumble I can put down to something in the drive train being out of balance but bounce?

The only difference I can see is in the tyres.
Bouncy has new Goodyear Wrangler M+S (which look like average road tyres), smooth has Cooper Discoverer A/T (which look much more chunky).

Do the tyres make this much difference?