Okay, so this debate has been rehashed a million and one times, but I always love hearing what people prefer. Do they prefer to do as little training as possible, with much of it high intensity? Do they prefer a lot of high volume training instead, with the intention of building resilience and durability? There are pros and cons to both, and I've gone through my fair share of coaches to have experienced the gamut.
Personally, it's hard for me to judge which is the best for me as no matter what you throw at a relatively young body with relatively little experience in any of the 3 sports, you'll garner improvements. In saying that, there's definitely a training style that I "prefer", in terms of life enjoyment. It's not all about the races, it's mainly about the training as you're training 95% of the year and racing maybe 5%?
High volume, low intensity: OMG, I can go forever like this, I just barely improve. There's definitely pace work in here, but it's more Ironman watts, ironman run pace, etc etc. It's great if you can include location adventures as there isn't much in the training that requires specificity, but damn, you're tired and not necessarily improving by leaps and bounds. I did this under the #teamhpb Hillary Biscay program and... while I improved, I found there should be so much more to it.
High-ish volume, with intensity: LOL, how my current coach Nicky Samuels recently started me off nearly a year ago now. Pretty much, I could do it and was excited to do it as I love high intensity painful huge bang-for-your-buck training, but I would SERIOUSLY crap out after 2-3 weeks of it, needing a break. Total loss of motivation to train, total exhaustion, throw your hands in the air "fuck it!" style. Still with Nicky Samuels but training slightly differently now. As an Olympian with far more experience, SHE can handle that load and more, but damn I definitely couldn't, not yet. ~Learning process~ for sure!
Low volume, with intensity: I never experienced seriously low volume (less than 12-13 hrs a week) but just over that amount with a British Level III triathlon coach. It was great in that I was mentally fresh, garnered minor PBs, the intensity wasn't hardcore, and had time to breathe. However, given the low volume, I couldn't exactly say the body was durable, resilient or strong. Just capable. So... really depends on what type of course you're racing. In saying all this, I definitely recommend low volume with some intensity as THE way to train when coming back from injury, burnout, overtraining or anything of the sort. This is what I did after I took quite a big break after anemia and overtraining double whammy (and a bike crash!) and it was the best thing for me. I enjoyed the sport and I improved without being overburdened by fatigue/high volume.
Low volume, low intensity: Ha! I call this the off season!!