I know the question was rhetorical but … the answer as always is, it depends. Depends on what? On what trade-off(s) you want to make. Yes, didn’t your mother tell you, there are always trade-offs in all aspects of life.
How many times have you read on this and many other websites: “What’s the best antenna / HF rig / Morse paddles /etc ?” There is no single correct answer when there are many slightly-different solutions.
One trade-off dimension in SOTA is radio performance versus convenience/comfort/safety of hillwalking. Most of us move along this scale for different occasions. Solo-activating a 10-pointer in harsh winter weather I would usually be at the comfort/safety end of the spectrum and take only a 2m FM handy and whip antenna. Participating in an all-day SOTA event on a 4-pointer in warm summer weather, I might take several elaborate antennas and multiple rigs. For most activations I’m somewhere in the middle: I want a multi-band HF antenna that’s quick to deploy even though it’s not going to give me ultimate Dx.
So, this debate about the ‘best’ coax feeder has to be set in context of your expectations. I’m with Andy @MM0FMF on RG174. My rucksack [especially in winter] is packed with winter clothes, bothy bag, lots of food, etc so space and weight are at a premium. If I lose half an S-point compared to using the ‘best’ coax, that means nothing if I can fit everything in the rucksack and still get a large number of contacts.
BTW: regarding RG174 losses on 10m, I find propagation conditions are more important than power level. If 10m is ‘open’ then it makes very little difference if my KX2 puts out 10W CW or 7W CW, where as if conditions are poor, 100W up the spout won’t help you. No, I won’t carry a ‘better’ coax cable just for 10m.