My personal opinions
Steel and iron Allomancy are, in general, worse than the surge of Gravitation, the advantage of Pushing/Pulling at range could help if the Radiant was wearing metal, but I think Shardplate would interfere, and would be too invested to affect without a lot of effort. Gravitation is also likely more efficient, because it basically uses gravity as a power source, while Steelpushes have to apply acceleration directly.
Plate and Blade would be better than pewter Compounding, while pewter would probably give more strength, this battle isn't likely to turn into a wrestling match, add