Comparing the two lamps that I found first, at close range, the P90 has a less intense (white) but larger (more oval) beam compared to the P61 with it's more round, brilliant intense beam.
At medium range I noticed that both beams were about the same brightness although the ovalness of the P90 was evident.
At longer range, I noticed that the intensity and smaller beam of the P61 illuminated better then the flood of the P90.
I compared both in Pyrex Standard Bezels using fresh SF123As.
I expect the P90 will maintain it's output for far longer then the P61.
For three cell SureFires, I find that the MN10 and MN11 of the M3 are brighter and more intense but more oval compared to the P90 & P91. The HOLAs are more round in both sets of lamps I compared.
Al