I don't know if this will be useful to the OP but I constructed it this AM just at open for a trade I was considering.
GIS:
Compare APR 37 short put with Apr 37/35 bull put spread with GIS at 40.06
naked short APR 37 put = put
37/35 bull put spread (sell the 37 buy the 35) = Spread
...................
Cash Return................Required Margin.............% Yield..............
Price.............put...........Spread........put.............Spread..........put............Spread.............Probability
30................(635).........(175).........3,635............174.............(17%).........(100%).................99%
35.................(128).........(175)........3,635.............174............(3.5%)........(100%)..................95%
40..................65...............26..........3,635............174..............1.8%...........14.9%.................50%
45..................65...............26..........3,635............174..............1.8%...........14.9%..................8%
Short Put
Expected Value = .5(65) - .05(128) - .01(635) - .44(381) = 32.5 - 6.4 - 167 = $-141
Spread
Expected Value = = .5(26) - .05(175) - .01(175) - .44(175) = 14.3 - 8.75 - 77 = $-71.45
By these numbers neither is a good investment but the spread gives you 8X the yield and is half as risky as the short put...i.e. you're likely to lose half as much. If you look at the Expected Value computation this is a result of the much larger loss for the short put at low prices. If I would cut the table off at $35 the result would be different as it would if I extended the table even lower. It depends on how much of recent history you find 'relevant'. This is not a remarkable conclusion it simply reinforces the nature of the trades and is well known and understood by (almost) everyone who trades options. You can read this exact computation in any of McMillan's books.