I think its more of a combination of the two. I have a loop I drive threw that has stop and go, hwy, and a few offramps that I can really get on it with a straight away, and the backway home has some hills and stops on hills. The whole loop is about 20-30min round trip with traffic.
I think it would be wise to in the diff. conditions make sure you log the rpm/conditions for the 30 sec clip in these well rounded conditions...not just a 30 sec. clip. Maybe look at the time by setting a stopwatch (my cell phone has one) and going to that data area.
The more data in the more conditions that you can repeat with close sim. the better, just make note to focus on one thing at a time with the logs (ie. maftransfer, slopes, offsets, idle, ect.).
I agree with Greg about you use what is needed for a particular application
When dialing in your inj slopes, offsets and the like ............
You need enough Closed Loop data for various driving conditions to allow
EA to be fairly accurate with its recommendations.
sooooo
A long dlog would apply in that situation
I've used 30 sec dlogs many times in the past to pinpoint specific conditions.
Here is a quick example for you
I had a nasty lean spike when going from a steady low load cruise condition to
a max power WOT condition.
I'd get the car up to about 20 to 25mph in 3rd gear
tap the space bar to start the capture for about 2 to 3 seconds
go to the floor for about 2 to 3 seconds
tap the space bar to stop the capture
Much easier to analyze 15 to 30 seconds of data
rather than go through
megs and megs of data you'll have with a long dlog