Consider that 'snubbers' only briefly extend the impact time (total force imparted by) of an all chain rode. In moderate conditions its the catenary that dampens the total time of impact - reasonable. In the quite rare extreme conditions and when there is essentially no catenary, a few feet of comparatively low elastic 'snubber line' isn't going to make any effective difference in the amount of impact - one of PDQ's rationale basis for this thread. During those times Ill probably be at 10:1 of greater scope (on rope or chain) ... there probably will be catenary, at least between the gusts. ;-)
The only rational way to do this is to perform repeatable experimentation in various bottoms, use various scopes and fluke angles, apply sufficient 'break out' force on the anchor --- pretty much all anchor manufacturers and USCG, etc. have published such data. And then, use such info and your personal experience as your guide.
Also know that double braid and three strand nylon continually hydrolyzes (weakens) when in constant contact with water .... a consideration for those who sit on their anchor a lot while doing 'extended' cruising. Certainly galvanized steel doesn't continually 'break-down' & weaken to the same rate as water-wetted nylon.
As one who uses both all chain and a mix rode .... after a few seasons anchored in 'de islands' and mud holes to and from these places, and well knowing the hydrolysis - material strength problem with wetted nylon, I will tell you that I certainly replace more nylon rodes than I replace all chain rodes. In industry etc., nylon(N6 & N66) begins to hydrolyze 'severely' and begin to significantly 'particulate' after about ~6 months of contact with water. Have you priced 'quality' nylon anchor line lately? ;-)
As regards the comparative weights of chain vs. nylon .... does it really matter to add an extra 1-200 lbs. to a cruising boat thats probably already 2 or more inches deeper in the water because of the typical stores aboard when long term cruising? I haven't cut the handle off my toothbrushes, etc. to save weight since I was actively backpacking; nor do I cruise with empty fuel (100 gallons) and water (100 gallon) tanks, only have 3 days of lightweight snack food, nor do I inspect and weigh everyone's 'permitted gym bag' for clothing .... all to save weight.
When Im PHRF racing my crab-crusher ... I might leave the all chain rode at the dock and have mostly empty tanks, etc.
For me, I prefer all chain so that when I inadvertently wrap the chain around a coral head or cochina rock (fossilized shells) during a real blow, I don't give a damn. ;-)
There are a number of false comparisons here, all of which will lead back to the all-chain practice. As I said, for my last boat I used all chain and liked it for the traditional reasons. This was supposed to be a thought exercise, not an assault on traditional practices and reasoning.
a. A snubber can offer a LOT of shock absorption. I consider a snubber to be about 30-40 feet long and quite elastic. The typical 6' snubber is simple a fiber chain lock. This is obbvious to me, since multihulls always use bridles.
b. I have performed such scope/break-out testing and it has been published. For pure load testing, the rode is straight and the pull is slow, so the material is not very important (unless we consider diameter--thinner is better). As for chain vs. nylon in dynamic conditions, that is far to complex for simple analysis (I have published it). In general, chain will do well in deep water, and nylon will do much better in shallow water.
c. Weight. Yes, a few hundred pounds would matter in the bow of a Stiletto 27 or F-24. 50 pounds would be out of place and noticeable to the keen eye in terms of pitching. This thread was not targeted at the typical lead mine.
d. Hypothetical. The question was "what would you do if there was no chain." Well, what do you suggest?
On answer is a free floating chafe guard not totally dissimilar from that used on dock lines. I've been testing some webbing/Dyneema hybrids that wear 20x better than nylon and better than steel cable. I'm curious for fresh ideas. Old ideas work, but are , well... old. As I said, I've used all-chain for decades and you don't need to sell the merits to anyone.
So, what would you do if you couldn't use chain?