I've always stuck with the 3-element lenses (preferably coated ones) because they are cheap and easy to obtain through ebay.
So far I have only found G2 lenses (uncoated ones mounted in barrel from one seller minus aixis or dtr).
I read that the G9 lenses are only sliiightly better or if as good as a G2/G1 lens but the G9 lens can be cheaper because they are attached to some factory mount to diodes in a certain bar or something.
DTR sells them.. 5 for just 25 dollars but they need to be put in a barrel which I assume isn't that easy because you'd have to cut the lens to even be able to put it in a barrel.
Is it really worth using a G9/G2 lens and are the gains of using one really that significant? I saw measurements on LPF where sometimes having the G9 or G2 lens can yield an almost 1watt power increase over the 3-element. Would it also negatively affect the corrected beam shape or are there any other trade offs?