I have a couple of pairs of SS5s, will dig them out.
I have some Gravel Kings, but on a GT Strike Road bike... hard to make a comparison with a 2.1 mountain bike tyre! but I'd guess that the Super Yummy's would give a bit more grip at the expense of rolling speed... but that's just a guess though!
There's also the price to consider too.. A pair of Super Yummy is 2.5 x a combo of Smoke and Dart...
How does the tread compare on the Supper Yummy to the Gravel King, my partner has the 700×35 on her Cross bike and its only a little shallower than my 26x2.1. So if you were to tell me they're not much deeper it's probably not worth it right now.