Simply it is a risk, reward equation. Hybrids offer a level of predictability in realation to capital value. No growth and as long as the underlying remains viable (within certain convenants) you get your capital back. Income levels again are set at a margin above bbsw an are not typically as volatile as equity.
In short (imo only) they are similar to bonds in structure but take on more like equity in relation to risk. I play frequently with them when they trade at discounts to face or to peers.
