From my prospective, three factors are interesting when looking into coax.
The shieling, attenuation & impedance.
Here a with the mentioned coax comparison:
Shielding
RG 58/U (20AWG) - 78% coverage with Bare Copper Braid Shield
RG 174/U (26 AWG) - 90% coverage with Tinned Copper Braid Shield)
RG 316 (26 AWG) - 95% coverage with Silverplated Copper Braid Shield
H155 - 100% Duofoil + 80% coverage with Tinned Copper Braid Shield
Attenuation (dB/100 meter)
Coax 10 Mhz 20 Mhz 28 Mhz 50 Mhz
RG 58/U 4,5 6,5 -- 10,4 (50 Ω)
RG 174/U 9,5 13,5 -- 18,5 (50 Ω)
RG 316 8,2 17,0 19,2 (50 Ω)
H155 3,0 4,2 4,9 6,5 (50 Ω)
This summer I change all my coax from RG 58 to H 155.
So far, I am pleased with the change. My noise floor went down by 5-8dB depending on the antenna.
The cost for the H155 is almost double, compared to the RG 58. However, in my situation it was worth it.
A must in my opinion is also good grounding of the coax shield and a common mode choke in each coax line.