I have cables, chains and U-locks. If I leave my bike for a short time where I can see it, I use a combination 5/16" cable, it's light and fast to use with no keys and I think I'll notice if someone tries to cut it. If I need more protection, like leaving my bike in the street for 2 hrs where I can't see it, I lock it with a 3' 3/8" case hardened chain and armored padlock to a steel post/big tree, and I lock the frame and my front dynamo wheel (the rear is nutted IGH). The U-locks are the least used because they are less flexible (can't use a big post or tree, etc.). On rare occasions I use both the chain and a U-lock.