Most important technical aspects of speaker wires? Capacitance, inductance, etc...

Looking into speaker wires, and technical specs or construction stated by companies, has anyone determined, measured of figured out WHAT are the most technical parameters for picking speaker wires? Is it Capacitance, inductance, gauge, insulation, construction, material used, shielding, etc...?

I do not buy thousands of dollars in speaker wires, specially for my $5K setup, but within reputable speaker wire companies being Furutech, Cardas, Audioquest, Nordost, etc... how would one pick wires? Obviously listening is the only real solution, however, many have to be broken in, not everyone has the options of trial, and it's a difficult task to complete if you're looking at multiple manufacturers, and various brands within each.

One last question, the outer sleeves used on high end cables, are they at all necessary outside of looking nicer?
It is hard to choose where to start.Listing your amp a ,speakers and budget will help get you some brands to research further.
The outer sleeves add only pennies to the cost of that was your concern.Sometimes it is necessary depending on the particular construction of the cable.
There are some superb reasonably priced cables out there.
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Thanks. About Synergetic Research cables. I’ve never heard those, BUT, attended a demo session by their rep or maybe even owner at AXPONA and found him to be incredibly sleazy, snake oil salesman and biggest BSer I’ve encountered in my entire life. Like they would do an A/B comparison and literally there’s no change in sound and he would BS something and convince ppl that they heard a difference. It was shockingly deceiving and just due to that session I was beyond turned off by anything they sell. As far as I’m concerned they're a bunch of crooks!  In comparison, Audioquest did another A/B comparison of their latest speaker wires and holy crap did I heard a big difference and they still didn’t boast as much as that sleazy guy at synergetic research. 

Now, I may have to try for myself to see if their speaker wires are any good and not snake oil but that demo literally made me question the entire company. 
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For 23 years I used Mogami Blue Neglex 2477 coax OFC 12 gauge to connect to my KLH Nine electrostats. 20 feet per side. I bought it cheap from my friend and local HiFi dealer - who received it as a sample. It was a 40 ft piece that I cut in half - cost was $40! SQ was excellent - never felt the urge to change for something else!