Wow, what a crazy thread....
Is M105/UF-SE the ultimate two step?
Absolutely not, because there are so many variables that come into play. M105 is an aggressive compound, so you wouldn't want use it on paint that doesn't need it. Also, it does have gumming issues if not used properly. However it is the heaviest cutting, nicest finishing compound I have ever used, and nothing to date works faster. To the poster who suggested M86, I see your point, but the main advantage of M105 is the fact you can cut a seciton in 15 seconds or less.
Adding OP or using M86 negeats that advantage IMO, which takes away from the time saving aspect. I disagree with M105 being the flavor of the month however. It is a huge time saver when cutting is needed, and used properly. It also leaves an very nice finish for on many paints (if not worked to long) that MAY not require a third step in the goal for perfection.
SIP/106ff have extermely long working times, and require about 45 seconds (I am being very general in this statement) with a rotary polisher, to fully break down the sharp abbrasives and "flash" the product off. For best results several passes should be made at low rpm after flash to ensure that no minor abrasions could be present. 106ff espically has a lubricant carrier that is very hard to completely remove, and like Ryan (rydawg) I test all my products in the most extreme conditions.
Leaving paint in the sun unprotected, wipe downs with numerous products (prep-sol, APC, degreaser, dawn washes, 50/50 alochol wipes) etc... Infact Ryan and I discuss often, as well both feel with out this knowledge, we have no bussiness working on vehicle's for money. It is our job to ensure true perfection. As Brian stated, that PC video is completely wrong. The difficult to remove carrier in Menzerna 106ff will mask the pad abrasions that common with oscilatting motions of the PC and improper working of the polish. It really needs to be worked to "flash" then burinished, and this takes much longer by porter cable.
As far as UF being the best finishing polish? I suppose its a matter of debate. Saying 3M UF-SE is worse because of its background is no differant, IMO, than saying Menzerna is bad because it was developed for certain paints with high cermaic content (referring to SIP/106ff). In my experience, one can never have too many polishes, and everybody will have a favorite.
I prefer 106ff on harder paint systems (Corvette, M-B, Audi, etc) because the sharp abrasives finish the paint extremely well.
I prefer UF-SE on softer paints as it is less likely IMO to instill hologramming or "mask" pad abrasion. UF leaves a nice gloss and a perfect finish when used according to 3M's directions, and I have never found it to have excessive cut.
I also have used M09, M80, OP, SIP, FPII, FP, and many other polishes for finishing. Of those, I would rate UF-SE as good as any, but with the extreme ease of use and lack of defect hiding (in Ryan and I's torture tests) it tends to be the first finishing polish out of my bag.
Hopefully this discussion will stay informative and not turn into a war.