In my experience, the ring bulbs may be a bit brighter, but have a very much shorter life.
The HID question has been covered many times before. To be strictly legal, the car should be fitted with a self-levelling headlamp system as well as headlamp washers. However, as far as the MOT test is concerned, only the operation and pattern are checked; if the lights work and the pattern is within limits, it cannot fail. There is (currently) nothing in the MOT manual about what type of bulbs are fitted. If you were to fit non E-marked bulbs this would also be technically illegal, but that is not checked by the MOT test either.
HID's work well in the GTV (as opposed to 156 etc) as the pattern is far more accurate/defined, being created by a lens/mask arrangement rather than simply a reflector. This means that there is virtually no "scatter" to annoy oncoming drivers.