For ice nothing will feel as safe as studded tyres. Soft (i.e. low pressure) knobblies are next best but will still feel skittish if they hit a big patch of ice.
For compacted snow studded tyres still best, big knobblies will be good too as they get a chance to bite in.
For uncompacted snow big knobblies are best, studded tyres don't give much more grip than normal "city" tyres as there's nothing for the studs to grip into.
For ice nothing will feel as safe as studded tyres. Soft (i.e. low pressure) knobblies are next best but will still feel skittish if they hit a big patch of ice.
For compacted snow studded tyres still best, big knobblies will be good too as they get a chance to bite in.
For uncompacted snow big knobblies are best, studded tyres don't give much more grip than normal "city" tyres as there's nothing for the studs to grip into.