It all depends on where you are using this light. For indoors I wouldn't do it personally.
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I've been using the X300U indoors for a while and it's fine. I wouldn't want to go back to 170.
I used to think not, I played with it in the house never had a problem with blinding myself....until. I decided to try it in the middle of the night, you know, eye adjusted to dark, a little sleep in your eyes, wow blinding yourself doesn't describe it. Not sure how adrenaline would affect all that.
I have a 300U that I keep on my rifle, but have a holster for the light on my 226 that I use on occasion as well. I have been trying to find a compact light that I could use on something m&p9c sized, and have a couple of the Crimson Trace lights (the railmaster and railmaster pro) which are both 100 lumens. There is a significant difference between the two and even indoors with white walls I prefer the 300U. Looking down the main hallway in the house (about 20 yards or so from one end to the other), the 500 lumens is a (no pun intended) night and day difference. 500 inside has not been a problem for me.
On my KAC SR-15 and FN SLP, I use Surefire X300 Ultra weapon lights. For a rifle and shotgun, the X300 Ultra controls have been preferable to me, the 500 lumen output is great, and they have been 100% reliable. For my Glock 19, I run the Streamlight TLR-1 HL. Because my G19 is my EDC, I often attach and detach the TLR-1 HL based on need, and I find the mounting system to be quicker to deal with. Similar to the X300 Ultra, it has been 100% reliable after heavy use, and the high 630 lumen output is helpful.
All in all, both options have been great thus far.
I use Surefire X300U on my HKs and my Glock. I have recently started using a TLR-1HL that I got at Christmas on my VP9, I am liking it also. The beam and spill on the SF is nicer than the TLR but the TLR is definitely brighter-which is actually a disadvantage because it is blinding when used in a dark room. I also use the X300U on my ARs. I like the actuation of the switches-works well for me on both pistol and the fore end of my carbines.
I have TLR-1 on my G23 and I also pocket carry a Streamlight Protac AA. Very good combo, the protac has been used and abused. I even bring it in with me to work (a county jail) when I know I am doing searches and need a compact reliable light.