Ok, so a worked example of the house favours underdog system from the campaign document.
Matt has both higher rep than me and higher crew rating than me for the game so I am eligible to use the difference on more than just the standard one extra tactics card per 100 creds. His crew rating is 1085, mine is 975. Difference of 110. However I must use the first 100 creds on a tactics card as usual. So I have all of 10 left to spend which is insufficient for anything.
For another example, let's pretend his on table rating was 1300 to my 975, in that case I'd have (1300 - 975) 325 creds in my favours pool. The first 100 would have to go on a tactics card leaving me with 225 to spend on other things. However only half of the pool can be spent on extra models that will appear on the table so I'd only be able to spend up to 163 on hired guns etc. Given that I'd probably spend it on a second card (100) and a hired gun or two worth up to 125.