Trade Check answers a tournament question: if I engage this unit against that one, is it a good trade? It simulates 3 000 rolls with both sides resolved together, so wiping the enemy means taking nothing back, and it shows the damage wasted on overkill — often what decides the exchange.
All 37 armies are there, from the BSData catalogue crossed with the Munitorum Field Manual. Trade Check needs JavaScript: the simulation runs in your browser, not on a server.