Is it better to ....

if you expect the odds to lengthen lay to back
...........................shorten back to lay

What im saying is which has a better propensity to win with? its not about using a judgement im looking more at fact?

How "simple" do you believe horse racing is?

Each race/horse in that flaming race needs to be rated on its factors in its favour and against it for the distance/type of race/time in season/going etc etc etc etc etc etc ........then their are factors like is it a front runner....or does it get held up etc etc etc

Your question is just inane!

Your question demonstrates you have little understanding of horse racing......IMO......

It will be better for you to back rather than lay.
It will be better for you to back horses at the front end of the market.
You will be unable to win either backing or laying.