[madformac]

Here's my take on this as these two are my favorite guitarists anyway.

As far as vocal range is concerned Lindsey has it it the bag. MK's vocal range is fairly limited, although he uses what he has very well.
Both of them produce and arrange music as well, I would give Knopfler the edge here because although Lindsey's skills are amongst the finest, Mark Knopfler has written and produced numerous film scores including Local Hero and Wag The Dog (starring Anne Heche, if Lindsey is reading this!) and his latest work was on the new TV series of Auf Wiedersehen Pet over here in the UK. Lindsey's approach to arranging is amazing though, I have to say.
As far as guitar technique is concerned Lindsey uses a Travis picking style (three fingers and thumb with the thumb driving the bass and rhythm) and sometimes "frails" the strings, a la banjo style with his fingers as well. Knopfler uses what seems to be a kind of awkward style with his thumb doing the majority of the work and using his fore and middle fingers, looking like they are glued together at times to pick the top E and B (thinest two) strings. His palm seems to stick close to the guitar bridge at most times too.
I play with a style similar to Knopfler's although I do move my right hand a lot more than he does and I do sometimes use my ring finger as well. It works for me.

Both of these guys are self taught and neither ever had a lesson which explains their unorthodox styles when playing electric.

Both guitarists play amazing instruments. Lindsey's Turner 1CLB is quite incredible for a single pickup guitar. Knopfler's Pensa-Suhr (see my avatar) is also quite ridiculous with it's range of tones.

***Seteca, I eventually decided to get John Suhr to build me a guitar similar to the one he built MK instead of getting a Turner 1CLB.***

Anyway, I think there really is nothing between them as artists. Knopfler seems more well known which is odd because Fleetwood Mac are far bigger than Dire Straits ever were.
I personally would give MK the title of best player only because I have seen him play things that I as a guitarist cannot grasp and everything I have seen Lindsey play I can understand from a guitarists point of view (even if I can't play like him! Ha!)

Hope this long, pointless ramble helps!