Never heard of irish linen be more slippery than wrapless. You are talking about a bumpy uneven surface vs a smooth shiny one. If you have a very smooth double-pressed linen wrap (which I do on mine and it looks and feels almost like leather), you can get almost any cue repair guy to re-wrap the stick with a rougher linen.
Concerning the bolded part, it doesn't work like that. Just because a surface is "bumpy and uneven" doesn't mean it offers more grip. Think of sneakers on a shiny basketball court's floor. That floor is smooth and shiny, yet the sneakers will easily grab that surface that you think would be otherwise very slippery. Cover that surface with stretched cloth that has small fibers (such as linen), and watch the players slip and bust their *ss.
It has to do with the fact that a linen wrap is essentially cloth -- a single thread of which is pulled and wound on the surface, of course, but cloth nonetheless. It's designed for
absorbency, not for grip. In fact, the same style of linen wrap is used on javelins, and the reason why that is used, is for
release purposes (so that the javelin does not "stick" to the skin of the hand, but releases easily) and therefore easily flies out of the hand.
A gloss finish actually makes better contact with the skin of the hand, and introduces a concept of "tack" (meaning, "tackiness"). This is why a slip stroke is much, MUCH easier with a linen wrap, rather than wrapless (which actually tends to "stick" to the skin).
Players such as Efren, who use a very light grip -- where the cue is resting upon a single contact point in the hand (the second joint of the index finger in Efren's case) -- tend to opt for wrapless or high-gloss finishes.
Stack leather wrap, as mentioned, is as close to wrapless as you can get without actually "being" wrapless. I'm in the midst of replacing all the wraps on my linen-wrapped cues with stack leather for this reason.
Here's a good video that shows how a stack leather wrap is installed, and what it looks like as a finished product:
http://youtube.com/watch?v=EteSBoXm9bI
-Sean