I've had both the Manfrotto trigger heads. Still got one somewhere. Compared to a normal ball head, they are fast to use. That's it. No other advanatges.
They are hard to adjust for critical accuracy, and ultimate clamping power isn't great, even after you adjust it.
The best budget ball head I've used is the RedSnapper RSH-12 - bargain for £50. V smooth and accurate, nice to use. I have a Benro J-2 which is a bit better still, and lighter, but several times the cost. Benro B-1 is very good value. Some of the higher end Giottos are also good and well priced, not sure of the model numbers though.