Stormlight roughly increases strength 1.5-2x. I've actually compiled a list of relevant quotes comparing the two in order to solve this debate once and for all, but I've yet to decide whether to post it here or on Reddit. Anyway a good indication of the radiants strength is that they rarely do anything strength wise that could be considered superhuman.
So the first quote quite clearly shows it increases strength, the second one shows that although it is not an insignificant strength increase it's not enough for kaladin to definitively say his feat in jumping is greater then an ordinary man could manage. Seeing as the horse appears to be thoroughbred and that are at most 170 cm in height kaladin probably doesn't jump over a metre in height otherwise he wouldn't have had to grab hold of the pommel and throw a leg over. He could have just bent a leg and landed on the saddle sitting. Also jumping over a metre in height is starting to be quite obviously superhuman so there's that too.
There's other instances of strength increases but i'm not going to list them all.
now on to pewter
So given the above quotes and pewters ability to allow people to run as faster or faster then a horse (which is 50km + about 2-3x the average sprint speed of a person) pewter likely increases strength by a factor of 5-10x. It will vary person to person though because in the case of a lerasium mistborn seeing as they are capable of stopping a koloss blow they are likely 15-20x as strong as normal and that's a conservative estimate. The koloss by virtue of being twice as big as normal must be 8x as heavy by virtue of the cubed square law and since they have shown reasonable jumping capabilities and survived falls from reasonable height they are likely at least 2x stronger on top of that. Combine that with the fact koloss will have all there weight behind the swing of a sword at similar speed 15-20x as strong isn't unreasonable.
Lerasium mistborn aren't more then 2x as strong as they haven't been shown to be able to pierce copper clouds so hence a normal mistborn being half strength. i'm not entirely sure on the strength of plate but this quote gives an idea.
So for the punch delivered above, the end result sounds quite similar to the blow the pewter thug delivers to Vin. So given that the thug had the use of two hands and the plate bearer only had one i'm going to say he is half as strong. That would mean a lerasium mistborn and a man in plate are roughly equivalent in strength, with a normal mistborn being being half that strength.
So lets double check that by comparing jump heights and accounting for the weight of plate. Plate probably weighs 200-300 lbs, enough that your going to find it extremely difficult to move in. So seeing as there's a scene where Dalinar jumps 8 feet which is about equivalent to 6 feet in normal gravity that means if you take away the suit which is at least his weight he would be capable of jumping 12-15 feet. We see Vin jump 10 feet in a leap so it's not unreasonable to suggest a lerasium mistborn could jump 12-15 feet if they wanted. So these results are roughly the same as above and indicate plate and lerasium are on par with normal misting being half as strong (remember vin is stronger then normal hence her jump not being that close to half).
So in summary plate>/= to pewter which is > stormlight.
So basically it depends with regards to pewter and plate and stormlight is a distant third.
So which one is strongest? feruchemy clearly.
By the way if your discussing Allomancy you might want to state whether spoilers are allowed or move it to a different forum.
