MY COACH HAS TOLD ME FOR YEARS THAT TRAINING BY POWER IS DANGEROUS. Frankly, I was too cheap to buy a power meter and didn't want to hassle with one more device. Her warning was that training by power would disconnect me from how my body was actually doing. I like simplicity so this was easy to heed.
Understand, I only get "coached" a few months out of the year... if at all. I just can't handle the structure, it takes too much fun out of riding for me. But, when I'm really serious about an event (none in '18) I need her guidance and feedback.
Word has it, the reason the pros took to power meters early on was because with all the chemical enhancement that was occurring during the same time period training by heart rate became useless. Their heart rate data was no longer relevant. It was not giving them accurate feedback on what was achievable with their new found "unbelievable" powers.
Anyway, I found this article by VeloNews really useful in helping me understand the differences and advantages of training by heart rate and/or by power. It's a good read, very clearly written.
... thought you might like it.