Difference in performance:
The new single trim version is actually about 10g lighter so always a bonus. Having used both of them now, whilst they are very similar in actual cleaning ability, they do perform quite differently on the end of the pole. The dual trim does seem to splay slightly more easily and hence is better suited for high level work. I was using it at 40-50ft yesterday on an initial plate glass clean and found that it scrubbed very well with very little effort on the pole.
The single trim version, in my initial impression, seems to be better suited for lower level work as it takes slightly more pressure for it to splay out. The actual bristles are identical on both brushes, where the difference comes in is having the inner layer either shorter or the same length.