I use butyl for training. Several reasons:
For racing I always use latex.
- I train almost every day and I prefer not to pump my tyres every day or every other day - butyl usually lasts at least a week.
- As I train most days, I happen to also flat when the weather sucks. Latex requires more nursing when installing, which I don't have the patience for (or the finger warmth before they go numb!) when it's snow or 2C and rain.
- I usually use CO2 to fill up my tyres after I flat, which doesn't work well with latex.
For racing I always use latex.