Yes, I actually have both and it’s all about your back shape. For me there is no comparison, the XCurve works WAY better for me. I have a buddy that prefers the EVO Krux. XCurve has curved stays, Krux is pretty flat. It’s all about what fits your back shape better.
I was in the same dilemma as you so I ordered both to test them out on some training hikes. I felt virtually no difference other than the shape of the frames on my back when I was hiking loaded with 30 pounds. Both frames were very comfortable at this weight.
When I bumped up the weight of the contents of the packs to 50# and started another hike the curved stays in the xcurve hugged my back perfectly while the evo felt a little stiffer to me. The weight savings wasn't worth it to me in the end so I ended up keeping the xcurve. I really think it's imperative to try both so you know if the curved stays are going to help or hurt.
Hope this helped but in reality the best move would be to go to retailer that carries SG to try both on (if possible) or order both and try them on at home to get a feel for the differences. Big investment for a pack so I wanted to have my bases covered instead of regretting picking one blindly over the other.
I've had both and agree that the best move is to try on both. I have a curved back but prefer the Evo because the curvature of the x-curve seems to be designed for someone much taller than me (I'm 5'8). The curves didn't line up with my back so I found the Evo much more comfortable.
Definitely all about body shape. I owned original Krux and Evo. Painfully uncomfortable for me. My X-Curve is incredibly comfortable. Most comfortable frame I have used and list is huge.
I have recently purchased (end of May) an x-curve and an original krux to decide between. Rucking was stopped after a few 40# hikes with the x-curve about 6 weeks ago, no hikes with the krux yet. Hope to start back up 8/1. The thing I noticed with the x-curve was shoulder straps have been somewhat difficult to get dialed in compared to the guide lite and the upper part of the frame seemed to be off my back a bit. The krux definitely contacts my upper back more if I pull down on the load lifters. Other than that I am still basically undecided between the two.
I prefer the straight stays and a double stuffed lumar pad. I also didn't like how with the excurve i would hit my head on the top of the bag because of the way the frame goes forward at the top
I saw a you tube video where a guy was explaining the X-curve was a better fit because he had a big bottom. I mean it kind of makes sense.
This video :
I went right to Stone glacier headquarters and tried both. The guy at the front told me all about your back profile. Said 8o % of us the krux will fit best ,semi curved or flatter backs. The x-curve is made for people with more curvature in their back. They have frames with 40-50 pound weight sitting right there to try out. I tried both and bought a Krux.
Re "flat back" vs a "curved back"... I was told to stand with my back against the wall. If I can fit my hand between the wall and the small of my back, I have a "curved back". If I can't, my back is pretty flat. Is that still the standard way to measure this?