Personaly, I think the choice of headset is such a personal choice that the question on which headset to buy is virtually un-answerable.
I started my PPL a few months ago and straight away I asked the same question. I had set myself a budget for my flying lessons and buying equipment. I added quite a bit on to my budget as I didn't expect to do as well as I did so had quite a bit left to spend.
At first I bought a set of cheap David Clarke headset in virtually the first week because thats what my instructor used, and then I inherited a set of Lightspeed Zulu 2 from my brother-in-law who failed his medical so basically decided not to fly again and let me have them. In the meantime my wife bought me a set of Bose A20 for my birthday so I ended up with 3 headsets. I also purchased myself some Sennheiser HME 95 due to the fact they were cheap, very compact and slipped easily in to my flight bag and thought that a passive headset would be great in an emergency and took up hardly any space.
Over all those months, I have equally used all those headsets and in all honesty I would say that anyone of them would be suitable for flying a GA aircraft (my ones being mainly Cessna and Piper). Even the cheap Sennheiser reduces the noise to far less than that I am exposed to from walking around the street.
But, everyone will have their own personal choice and to them one headset will seem better than another in one way or another.
I personaly prefer the ANR ones over the passive ones but only for the reason that with both my Lightspeed and Bose I can quite easily hear the stall warner whereas with the David Clarke I cannot hear it as easily. Also the ANR headsets just don't clamp as hard against my head.
If I was going to buy my first headset now knowing what I do then out of all the ones I have I would go for the Lightspeed by quite a big preference. I am not saying it is better than the Bose but it is certainly not worse under any test I could give them and with a £300 price difference between the 2 I really could not justify £75 for each letter of the brand name.
For what it's worth, this is my OPINION of the 4 headsets I have.
The David Clake I find very sturdy and I do like it. It does tend to become a bit uncomfortable after a while but not unbearable. It does a very good job of attenuation but for me, it also blocks out a lot of sounds that I very much want to hear. But I still think that this is an ideal headset if you are on a budget but still want a well known, proven headset.
The Sennheiser HME 95 I don't think is really suited for GA aircraft for regular use as the attenuation is not brilliant. But as I said, it does attenuate the sound to a lower level than if I was walking in the street and is fairly comfortable and compact. But for long term use I think it would get a little tiresome.
The Bose A20 is absolutely fantastic. It does have bluetooth which I dont really have a need to use. I probably would not have purchased this if it wasn't a present but that was really based on the cost of them. But now I have it, I really do like it. Attenuation is excellent as is comfort but as I already mentioned, I do think there are other headsets that are just as good but with a much lower price tag. But BOSE have established themselves in almost any audio market so are a popular choice at any price.
The Lightspeed I think is an excellent headset that I personaly would rate as good as the Bose but has a more reasonable price tag. There are certain resellers in the UK (not sure if I am allowed to mention them) that are, at this minute, doing a very special deal on the Zulu for just over £600 which is £375 less than you will get a Bose A20 with bluetooth for. I find there is absolutely no difference in comfort or noise levels between the Bose and the Lightspeed and would be just as pleased with either one. In-fact, I find the Lightspeed does actually have one advantage over the Bose and that is in respect of passive attenuation. or me with both headsets turned off with no ANR, the Lightspeed does a slightly better job than the Bose. Also, I like the fact that the Lightspeed comes with a very good, quality case that protects the headset a lot better than the Bose case supplied.
Anyway, as said, these are just my persoanl opinions and someone else could have these exact same headsets and forma completely different opinion.
Steve