GO to Target, and next to the X5 that's hanging there for $25 or so, there should be an Inova XO for around $35. It's like night and day the difference between those and that XO light is a cool 70ish lumens (as bright as my TLR1 weaponlight and a little more light than my P3D's medium light.
But then, if you want some serious bang for the buck, just pick up a Romisen from DealExtreme. Orrrrr...get a nice R2 5 mode drop in on a $35 SF G2 Nitrolon.
The X5 is best used in the car for maps and things dropped on the floor that rolled under the seat. Lighting tunnels/sewers..not a chance.
I wouldn't let those differences be the deciding factor between the two lights. For one, there is enough variablility in the lights that a PD30 could be brighter on all levels than a P3DQ5. Sometimes you just get an overperforming light. Also, many of those differences are within ten lumens, and most likely can't be seen by the human eye.
In my opinion, the decision should be made based on the switch type.
and what is the different types of switches?
My favorite light ever is the old Inova X03/T3 with optics. Highest quality light I have ever had the pleasure to use, and I've used a lot of lights, Surefires included. You can get one of these at the sales page at Batterystation for $45 and it comes with 12 free batteries. It is the perfect brightess, and good throw, but the runtime is not great by current standards(2.5 hours). If you will mostly be using the light in cramped spaces, I might go for one of the newer Inovas, which have less throw and more flood. Or, with a budget like that, you could get a Surefire and use a lense diffuser.
What is it that you are doing in 100+ year old places under NY anyway? Are you some type of construction worker, or are you just exploring?