They do compliment one another well, lets hope their love-child is as accomplished as either of its parents

 despite appearances they are very different beasts altogether.
So heres a quick account of what each frame has that the other doesnt.

Surge:
411mm chainstay length (vs on the surly 416mm slammed SS/425mm QR/420 with 142x 12mm)
short 16in ST for slamming saddle & low standover.
can case a 20ft gap jump without flinching (still my a*shole may flinch)
has stealth routing/guides
short flickeable fun & agile
in summary a monster dirtjumper with allday capabilities.

Instigator:
clearance for 3in tyre (sorry lol had to point that out)
30mm bb drop so can properly take a 650b or 26+
bosses for 2 bottles (surly has nowt)
short headtube for low front end
18in braced ST - firm & supportive at proper ride height.
605 TT (vs 585)
compliant rear triangle
E.D anti corrosion treatment
in summary its extremely versatile adventure bike that jumps well with solid & low slung geo.

 in time i would guess the surge will be replaced with FS. maybe. this hobby is about acquiring bikes not loosing them

 wise words, i now own 4 for the first time ever (nobody's bought my Capra yet though )

 You wrote all that and yet didn't answer my question.. god I love you...

 He did though ,the NS

 open to interpretation but well he didn't ask if i wanted to get shot of either...
dont mean to bite your style pigman but the surly bears something of a resemblance to the trans am, even have rsc polished about to go on - what you make of em?? have guide r on the surge & have had zero issues with performance, levers getting a little rattly..

 I have a set on the YT and xo on the Scout, I really rate them with uber race matrix pads, stop my lardy arse no problem. Surly looks straighter I think ,lovely bike BTW

 Ta & good call on the race matrix. another reason wanted the trail/guide caliper was for bulk buys. tried any of their other compounds?

 A few mates prefer their sintered, I tried Kevlar but matrix are by far my favourite

 roger that. think ill order up some to try.