I have an XTR rear mech on my bike and its lovely (compared to my LX rear mech) You can really notice the difference….

but, I need to remove the rearward loop from the back of my frame so it fits in my car boot better and so I stop ruining the rear mech outer by not bending it all the time to fit it in the boot.

If I'm going to spend a bit, I would rather the new mech be as good as the xtr.

X-7 or X-9 (x-0 is just daft money)

get an xtr shadow, X9 is good but X0 for the pimp factor

X9, X0 is just too much cash for something you will prang.

XTR shadow rear mechs have a similar cable run to Sram

Or just unhook the outer cable from the chainstay/seatstay?

to be honest I have run an SRAM x5/7/9/and X0 and if I did not look down I could not tell you which one was on the bike.
I can lend you and X7 I keep as a spare to try but you will also need to change shifters.
iirc one model works with shimano cant recall name

http://www.pinkbike.com/video/15232/

shows why SRAM are better
the only difference between the numbers is the materials used not the actual design iirc

XTR shadow

third for the XTR shadow. The pivots on X9 mechs go all loose and wobbly after a few months in the peak district. No experience of X0.

Believe me there is no Sram mech to match XTR

Really there is nothing between shimano and sram both produce decent products that are used by pros and top amateurs. That is an interesting video from junkyard though don't know what conclusions to draw from it. What I would say though is run either full SRAM or full shimano set up.

I'm a big fan of the way the sram stuff works but switching seems an expensive way to get rid of the loop of outer as you'll need new shifters too. A better way would be to get a shadow mech or just get an Avid Rollamajig though you may have trouble finding one now.

Why would I need new shifters to switch to Sram?

does sram move less / more per mm movement of cable then Shimano?

😕

Yes. Sram rear mech's only work with Sram shifters (Except Rocket & Attack, which are Shimano compatable) Front mech's, doesn't matter what shifters you use.

XTR shadow it is then Dear as it may appear, Its still cheaper then new shiferts….
Saying that, maybe its just cheaper to keep snipping the outer back.

SRAM = 1:1 actuation
Shimano = 1:2 Actuation

Front mech both are 1:1

Rocket and Attack are shifters only not mechs
I dont think SRAM do a 1:2 mech.

having had both. sram hands down. you should be able to pick one up on feebay for between £45 and £70 dependant on age and condition. then get twist grips for £50 brand new. you wont look back!