Dont know where those of you live who seem to be only using a U lock. I know the OP was wanted something that met being light & handy.
But if I limited myself to the the use of only a U lock I would not be able to lock my bike. But......

The bikes I have mean far to much to me to be in such a hurry, or inconvenienced that an an extra few seconds locking it up best I can, causes the same level of grief I felt when looking at the now empty place that just prior, was my bike.