Yes, well of course I do like to promote TTL as a genuine choice. Lets expand this idea a bit, because as always it depends entirely on the circumstances, lighting environment and nature of the subjects. So my statement relates to mainly static subjects with consistent or no ambient light, and where there is none of the typical sorts of intrusions that we expect to disrupt TTL flash metering (bright areas in backgrounds, light spill into the lens, reflections etc).
In these sorts of stable conditions then I have found that I can use TTL mode in very much the same manner as Manual, and without any significant difference in technical / workflow approaches. The advantage with TTL then becomes nothing more than it avoids the need for any mental reckoning or other calculation about a starting point for the power settings. After the initial test shot then the adjustment needed to each group is exactly the same as an adjustment following assessment of initial test shot in Manual mode. So I am just saying that to all intents and purposes the Cactus system has eliminated all significant differences in practice.
Of course there will always be those particular types of scenarios where TTL will remain more suited, and also Manual mode.
---------- Post added 23-10-18 at 00:25 ----------
Some examples of the sort of situations which are static where I have found TTL and M mode to offer no significant point of difference are the recent threads I have posted here;
Lighting Control for Flowers - PentaxForums.com (mixture of normal and HSS TTL), and some portraits of the kids in the garden
Contrast Control in Sunlight - PentaxForums.com .... /....
Lets Get Outdoors With Some Radio TTL! - PentaxForums.com.
---------- Post added 23-10-18 at 00:34 ----------
Originally posted by Class A I would have loved to try TTL with the RQ250 outdoors as that's when I may have had the need for quicker operation
TTL could be quicker, or it might not be. I actually suspect the reality in practice will end up depending on each individuals experience levels working with their equipment and the Modes themselves. The XTTL system removes most of the workflow / settings differences between the two modes, it will mostly come down to the person .... Imagine if only we'd got the RQ250 .... you might have been able to quickly dial in a manual power setting to balance the bright sunlight from one side .... and I might have been able to quickly set an initial compensation figure in TTL mode to do the same thing. The result could easily have been the exact same image in exactly the same time.