The 1-inch headphone plug was discovered yesterday by renowned audiologist Rod Biggums. When asked how he came up with the idea, he replied that having woken up early one morning after dreaming of a new tube amp design, it simply 'hit him in the face'.
most phone jacks, whether 1/4 or 1/8, are pretty flimsy and has very little contact surface. so i'm sure a well-designed 1/8 jack would best most 1/4 jacks. of course RCA and XLR jacks have better contact, and direct solder is even better.
I look at it this way: If I was to get a pair of headphones recabled I would go 1/8" everytime because if I did 1/4" and I wanted to convert down using a Grado or Senn adaptor I would be adding 6" of stock wire into the chain. I don't know if this would defeat the recable, but I would always wonder.
I think the 1/4" TRS and Mono TS connectors are carry over standards from telecommunications industries in the 40s. When switchboard operators would patch over calls. And Even that might be carry over from telegraph operators and military standards.
It just got carried over from other industries.
Personally I dont like either TRS because they short out the amp channel as you plug and unplug. I like locking XLRs personally. But of course you cant use that on a small portable.