Keep in mind that adding a lubricant to the threads (CLEAN threads, mind you...) does other things than just make the metal parts slide across each other easier.
Lubricants are required for certain conditions/materials and sometimes it really has nothing to do with torquing, per se. Stainless steel components, for example, are extremely susceptable to galling with metal-to-metal contact. This is why lubricants such as neolube (colloidal graphite suspended in alcohol) are added to the threads. Tightening/loosening CRES (Corrosion Resistant Steel, or stainless steel) components initially causes microscopic galling of the thread surfaces. This rapidly becomes visible galling with repeated unlubricated use. Eventually it can get so bad that merely attempting to turn the bolt/component in either direction will literally cause pressure welding of the galled surfaces together.
Lubricants are also added as thread protection against future corrosion while installed. This makes them easier to remove at a later date without causing thread damage which must be repaired before reuse.
Since it was brought up, "torque" isn't the force which holds the bolted components together. It's bolt tension felt between the angled threads and the head of the bolt. As
@redneck2 said, the force being applied to the bolt actually causes the bolt to elongate. It's the fact that this is an elastic deformation of the bolt material which causes the compression felt by the bolted up components. This elastic deformation ONLY occurs if the bolt actually turns while the torquing force is being applied...because it's the force of the threads pulling against the bolt head through the shaft of the bolt which causes this elongation. No turnie-turnie, no stretching.
Applying a lubricant will allow the bolt to turn easier than on dry threads...therefore it's easier to get that elongation for a given torque.
As I said earlier, the wet/dry torque requirements are typically specified in engineering drawings. But not everything we deal with has, or requires, that level of engineering specificity.
BUT...reducing a torque value by a given amount without understanding the engineering requirements behind it is not good. Every lubricant is different, which means the amount you may be able to reduce the torque value by will vary. And going by "some guy heard you should reduce the torque value by (X-amount) when you apply lubrication" may be a recipe for disaster when the components later catastrophically disassemble themselves under load.
SO...which is better? Wet torque or dry torque?
The answer is "THEY'RE QUALITATIVELY THE SAME"...with the caveat being "IF YOU FOLLOW THE ENGINEERING SPECIFICATIONS". If the engineering specification includes both a wet torque and a dry torque, either will provide the SAME bolt up tension if you apply them correctly.
If the engineering specification is "dry torque", then apply the specified dry torque.
If the engineering specificaiton is "wet torque", than apply the correct lubricant per the specified method and then apply the specified wet torque.
Here's an excerpt for nuclear mechanical joing make-up instructions from one of the shipyard procedures where I work:
"If no specific torque value is given in applicable technical manuals
and no guidance is profided for fastener lubrication, the fasteners are to be lubricated with graphite in isopropanol per MIL-L-24131. This is not to be confused with when a torque IS given, but no lubricant is specified. In that case, teh fasteners are to be torqued dry (see paragraph 3.2.9.2.5.3)."
"Per Submarine Overhaul Specification (reference 2.1) and Surface Ship Overhaul Specification (Reference 2.2), Sections 9090-3-b and 9090-3-j; 'Where class drawings specify torque values for fasteners without reference to the application of a lubricant on the threads, the intent is to torque the fasteners in a "dry" (non-lubricated) condition.'"
In the world I work in, these things DO make a difference. And we don't arbitrarily apply a lubricant and reduce torque values because of it without written authorization because of this.
In the world of mounting a scope onto a rifle, the same rules in general apply: if a torque is given with no lubricant specified, then torque it without lubricant. However, in THIS world, you are not likely to cause any direct physical damage by choosing to apply a lubricant and either applying the same torque OR reducing the torque to some lower value.
Rebuilding a 350 four-bolt main? Probably ought to know these details.