I've used some of the lamps from Digilight/G&P(6, 9, and 12V), Wolf-Eyes(3.7, 6, and 9V), and Lumens Factory(3.7 and 9V).
My Digilight and Wolf-Eyes have better beam quality than the SF P60s and P90s I've used, as well as being both whiter and brighter. I use rechargeables in all my users, now, so no longer have any 6V lamps. Anyway...
The Digilights focus down to a round spot, and have good spill.
The Wolf-Eyes have an oval spot that fades more gradually into the spill, and covers a wider area.
The Lumens Factory lamps are even whiter and brighter(even the low output ones) with more intense spots that are also oval. Better for throw, and cutting through fog, etc than the previous LAs, but weaker spill and poor overall beam quality.
I like, and use, lamps from all three of these brands. Four of my five incandescent lights are SureFires made for use with the P60 or P90, but I don't use any SF lamp assemblies, except a P90 as a spare, since none of these off-brand lamp assemblies will fit properly in a SF spare carrier.