When writing my book I did some limited research about the performance of using solely inline layers with one blade enabled in each (Firewall, APCL/URLF) vs. using a single layer inline that invoked the Firewall blade in the top/parent rules (simple services only), then invoked APCL/URLF in the sub-layers via categories/applications. For an identical policy goal, the resulting compiled Unified policy for each approach looked extremely similar and I wasn't able to detect any difference in rulebase lookup performance between the two. So my basic conclusion was that ordered vs. inline is about the same as far as gateway performance especially due to the new Column-based matching, but if anyone from R&D would like to elaborate on this topic that would be great. @PhoneBoy
My general philosophy is that if you still have the straight ordered layers (one blade per layer) which is what you end up with after a R77.30->R8X upgrade and they are working well for you, there is no urgent need to spend the time converting it into a fully unified inline policy. This is especially true in my opinion if the policy is very large. It doesn't seem to make a difference in gateway performance, but a properly-constructed inline policy can be easier to understand and work with.
However if you are creating a brand new policy package from scratch for a new gateway/site, I'd strongly recommend using fully inline layers from the get-go and possibly security zone objects as well. This is a piece of cake to do when starting a policy package from scratch, and will be much easier to manage in the long-term as the policy size grows.
Gateway Performance Optimization R81.20 Course
now available at maxpowerfirewalls.com