I don't own a G3, but it won't be any different than the 9P as far as beamshots. The P60 vs the P90 is no comparison. P90 kills it in every aspect. The P61 vs the P90 is pretty close. The P61 has a round beam while the P90 has an oval beam. I think the P61 is a little whiter in color but it's hard to tell which is brighter.
The P91, well that's just a different ball game lol. The only thing that comes close in the D26 range (or beats it to some eyes) is the EO-9 by LF. I actually prefer the EO-9 over the P91 in most cases.
I concur with Bryan exactly, however from a close range (handgun / Rogers Technique) combat light perspective, personally I would stick with the P91 due to the peripheral illumination. If you are looking for throw, the EO9 is a great choice.