To me, it is whether you want long or short pole hedge, whether you want articulation or not. This will limit you to one or the other, no need to talk which one is better.
If I have to vote for reliability, I would vote for Echo. I own two Shindaiwas and only one Echo. But from reading posts here for years, Echo has the fewest complains. There is no growing pain like a lot of the new models of a lot of brands. Newer Shindaiwas like T242 and T282 seems to have more complains unlike the old T260 and T270 and T230. Also the EB8510 has a lot of complains.
I personally have no problem of the Shindaiwas, but I have to say I am a lot happier with the C4 EB3410 blower than the M242. I had to buy the choke assembly because the old one broke and has recall or something. When I use the M242 as pole hedge, the filter always work itself into the neck of the tank and won't pickup gas. It is under power for 24cc in my book. It is not bad, but if I need another one, it is not going to be 242.
If I were to buy a articulate pole hedge trimmer, I would buy the Husqvarna. They have the short articulate version like the Shindaiwa. Echo should come out with a short articulate attachment. But that is just me and OP did not ask for suggestion for another brand.