I preferred the Gentle Leader to the Halti - couldn't say why. However we now use a Dogmatic - http://www.dogmatic.org. They had to specially make one for us as their smallest was still to big for our whippet, and they were fantastic about it!
We keep Gentle Leaders in the cars at all times in case we get caught out and need them. The dogs are funny, sometimes they are perfectly behaved and other times total terrors, so it always helps to have something handy. But I REALLY like the Dogmatics.
Wendy