The older Murmurs were really nice for light loads. Pretty easy to live out of too, which is important to me. But they were somewhat fragile. Too bad they quit making them. The new ones look much sturdier, which means heavier.
The Zero is very similar to the old Murmur, only made with Cuben and extremely light. I have a small Zero with only 2 water pockets and the pad holder. I use some light guy line cord as a sternum strap sometimes to keep the straps from moving around -- the Cuben can be slippery. I did not get any other options, because they defeat it's purpose as a minimal pack.
If the original Murmur was still available I would say get the pack that fits your budget. But you can get a Cuben Zero for close to what the new Murmur costs. I hate mesh pockets and would skip that. YMMV.
BTW, after several years of SUL and XUL hiking, I am pretty much switched over to an internal frame pack. Much happier and willing to have a base weight of 7 or 8 lbs versus 4 or 5 lbs.