It's a complex subject Josh and to add to it, consider the term of "anti trend". It's when a horse finished with a placing against heavily unfavourable conditions. Happens every day, that's why hardly anyone wins long term. The unfavourable condition can refer to many things: track bias, positioning bias, jockey, class...blah, blah.

For instance consider a favourite in a race noted as 'front runner'. It wins, so what could you put that down to?:

1/ The horse had better all round ability than any other runners?
2/ The race was a lower class race and most horses in that class don't have chasing power?
3/ The race was run at a slow pace and so the horse didn't burn up all it's fuel early on, so it's win wasn't so extraordinary?
4/ It's win was an act of randomness, after all one of the horses has to win?

So to be able to tick a box and go, "yep, front runner, certain field size, track bias and rail position suit, isn't so simple as points 2,3 & 4 could have a bearing.

By way of being contrarian, I'd be narrowing the selection possibilities down to looking for "anti trend" horses. A horse, that despite a history of this or that, overcomes those difficulties in a recent race and should be rated with more favourable consideration than a horse that performs to average expectations in past runs. In other words the horse that upset at largish odds last time out....have a closer look this time out??