I love my large SL carbine in grey/black. I’ve done about 1000 miles on it. I’m 5’9ish. Reach isn’t mega long, but it was 40mm longer than my old bike, and I think it’s close to perfect. I use a 170mm dropper with about 10mm of post body showing.
it’s an awful lot of bike. 33lbs with SG marys. However, it is so much better than the M 2015 tracer I had. MUCH stiffer and the JS enduro link is much better suited to chunky stuff. The tracer didn’t use its travel all that well. I’d expect the Primer to be somewhat similar in that regard – quick to use a big chunk of travel before ramping up too soon.
Buy the primer if you just need an amazing trail bike.
Buy the carbine if you want to race enduro, open up ALL of the lines and enjoy going really ridiculously fast over everything, and you don’t mind lugging the heft around.
My mate’s SB6 is nicer in many ways, exquisite almost, but I definitely wouldn’t have one over my carbine