Is it Chocolate Ball Sedum? Most Sedum is good for zone 3 to 9, though some will be "iffy" in zone 3 and will do better in zone 4 and below. If you don't think it is well enough established, be really weather aware and cover it if you are going to get a hard freeze, or mulch really well before winter sets in. I have to agree though, Chocolate Ball (if that's what you have) does look daintier than Angeline. I hope this helps.

Here is a link that might be useful: Chocolate Ball Sedum