I own a 1959 M-20. This was given to me last year by my cousin who bought it new in 1960. It is in excellent condition, virtually unplayed.
My first guitar which I bought in 1961 was a 1939 Martin 00-17. Sadly it was stolen around 1965, I'll recognize it if I see it.
I also owned one of the very first 000-15 models. MIne was unusual in that it had highly figured genuine mahogany ( not sapele) throughout. Though it was a decent enough guitar it was not the match of the 00-17. I sold it and yes it did exhibit a neck problem but these were mortice and tenon style joints and at that time Martin had not developed a technique of repairing them, they would replace but not repair. I sold the guitar to an official Martin Guitar repairman.
I much prefer my Guild over either one of those guitars. Lots of character and excellent playability and tone, not to mention that it's not just another MArtin.
I have owned a dozen Martins though none currently. Not likely to buy another unless it is pre 84.
I am considering other Guilds.. but guitars are case by case,, so I'll try a few and take my time.. Meanwhile I'll enjoy the M-20.