I have both of these packs and don't know if I'd use either on a thru-hike?
For me, both pack's have way to many straps, either for adjustment purposes or for load compression.
With the Catalyst, you have 4 adjustment straps (2) for the shoulder straps and (2) at the hip-belt. I guess that once you have these straps adjusted, you could leave them set, but I always seem to loosen them, and re-adjust them, each time I put the pack back on.
For a thru-hike, this would be a hassle for myself dealing with excess straps. I've heard that many get sick of them and just end up cutting them off anyway.
With regards to water bottle access, I don't really see how a spandex water bottle pocket would make it easier to remove and replace a water bottle. The Catalyst's mesh side pockets are huge, and will easily hold a 1 liter platty or Gator-Aid bottle, and IMHO be much easier to access than the Trance's side pockets.
I'd like to see the Trance, with side pockets like a McHale and a fabric front pocket, loose all the 1" wide webbing straps, and lower pad straps. Place some loops on the pack so you can lace some bungee cord over the front of the pack, and have only 2 side compression straps similar to a McHale or with only one per side like the Catalyst.
Also, the lumbar pad and hip-belt needs much design improvement as well. I'd like to see the Trance's hip-belt be a little more supportive with regards to load bearing, meaning it needs to be beefed up a tad more. Lumbar pad is too flat,and needs more padding and lacks grip as well.
The main hip-belt side support wings are also too far outboard from the hips, which lessens the wrap-around effect and snug fit that you should get from a hip-belt. Narrow their attachment points, so these wings exit the rear of the pack, closer to the lumbar pad, like in many packs where the hip-belt passes through or behind the lumbar pad.
Being the Trance lacks hip-belt load lifter straps, I'd possibly lean more to using it over the Catalyst,but it would be a tough call for me.
I think that with the Catalyst loaded properly, one could do without the adjustment straps, at the very least you could probably do without the hip-belt load lifter straps.
Sorry for the ranting, I probably didn't help you much, but I can speak from experience about using a pack, with and without any type of adjusment straps, and for me personally, I would not want to have any excess straps to deal with on a long thru-hike.
I'm not selling McHale packs to you, but I have a LBP36, which has removable side and roll top straps and that's it. No adjustment straps to deal with, just put the pack on and go!
Consider the ULA CDT, not much in the way of adjustment straps, also MLD packs like another poster mentioned. But this is a frame-less ruck, which although about as simple as they come, you would probably be carrying more weight on the shoulder's, especially through area's with less frequent resupply.
Hopefully you get more actual thru-hikers here, giving you solid advice, of which, actually,I am not.
I do have a ULA Catalyst,Circuit,MR Trance, Granite Gear Nimbus Ozone,McHale Chasm,and LBP36.....whew!!