I haven't posted this for awhile, so if you've seen this already, sorry.
I'm the guy that started the "super" kits when I ran Superior axle & gear. Here is a bit of background on the big spline Dana 35 Kits.
1. We developed the 30 spline kit for one reason only. The stock shafts were breaking quite often in any big tire, locker equipped application. We felt we could develop a solution for a Dana 35 owner, that wanted to run bigger tires and a locker with some reliability. For that very specific customer, we made the super 35. I think we accomplished our goal.
2. We did not (nor do I now with my new company) compare the strength to other model axle assemblies. We only compare to stock components. To compare to a D44 or 8.8 or Toyota is pointless in our specific goal of increasing the reliability of the D35.
I look at the question this way:
If all you really want is a reliable locker and axles in your D35, don't waste the money on a 27 spline unit. Go with a Super 35 or Grande 35 and be done with it.
If you want more overall strength than your D35 (gears, axles, tubes, etc.) then bump to a 44 or 8.8 or 60 or 9".
The cost comparisons have too many variables to be of much help - everyones situation is different. DIY vs. paid labor; already geared and just need axle/locker vs. need gears and axles/locker; etc.
Look closely at your specific situation, needs, future upgrades, budget, etc. and make your own choice. None are "wrong", just fit different peoples situations.