I think ultimately yes having the ATU separate is nice, but mostly so you can choose to be lazy! The main downside with the L817 is the batteries in the tuner make it heavy. Having external patch leads to juggle on top of that makes it a nuisance. On the other hand I can do 15M DX work if I take it on the trips 
If I were to do it over again I would have been more patient and saved for the KX3 with its internal ATU and max 15W in the latest firmware with enough power (See Elecraft KX3 - Increased Output Power with Latest Firmware Update ). It does really feel like the sweet spot for back pack HF from my perspective.
I guess the other rock to turn and without derailing the thread too much (there are oodles of antenna threads here) is that I’ve been really pleased with the SOTAbeams linked dipole on 20/40. That bit of kit I have never thought twice about.