IIRC they are 'softer' as they have less brisance than 616s. That gives them lesser/slower ignition qualities, it doesn't effect the ease/force with which they ignite. They tend to get used in slow ignition big and small bore shotguns.
FWIW this is a brisance rating that I copied years ago, softest to hardest. If your device favours a particular style of ignition for some reason it may be useful? Worth noting that the Euro primers are larger in OD than the US primers? Cheddite are pretty fat compared to Federal for instance.
1. Rem 209 STS,
2. CCI 209,
3. Winchester 209,
4. Noble Sport 209,
5. Cheddite 209,
6. Fiocchi 209,
7. CCI 209M,
8. Federal 209A.