I'd get something with Climashield XP. It's almost as warm per pound (highest CLO value) as Primaloft One (PLO), and warmer per pound than than Primaloft Sport (PLS). But XP will be more durable (retains loft) better than both PLO and PLS after stuffing it into a stuff sack 2.5 months in a row. And, XP doesn't need to be quilted to scrim to stabilize it like the 2 Primalofts do - so total bag weight is often about the same for XP as PLO.
On the other hand, Primaloft is a short staple insulation, whereas XP is a continuous fiber, so PL stuffs to a smaller size and this could be critical if you are carrying all the NOLS food, gourmet cooking setup, books, etc. PLO also drapes a bit more (is less stiff) than XP, but XP is no worse than 3-D was.
When I compare bags from different manufacturers, I'm usually looking at similar shells, shoulder / hip girth, and zipper lengths since I know how worried I am it will get wet (ie: tent vs tarp) and how hot it will be (no zip vs full zip). So, the difference in weight is essentially due to the amount of insulation (ignoring small variations in the curvature going from the hip to the feet different bags use). If they are the same type of insulation, then it's simple to compare the bags, otherwise you can use the CLO values for each type of insulation and calculate comparative warmths (search on CLO and you'll find lots of info, or goto thru-hiker.com and read the sales paragraphs on the insulation pages).