CPAP or DPAP - when and why?

I am curious as to which is used at other hospitals - CPAP, DPAP, or both - and when.
I have heard that DPAP is more cost prohibitive, etc. Is this true?
What are the factors in deciding whether you use CPAP or DPAP?

In our hospital, we use CPAP only when intubated and when apnea is a really signifigant problem. Otherwise, it`s always DPAP, advancing to N-DPAP after extubation. We NEVER use CPAP once the baby has been extubated.

Our NICU has a very low rate of chronic lung problems, and we almost never have babies go home on O2 or monitors. I am wondering if the CPAP/DPAP difference has anything to do with this. The head neonatologist just says "We use it because it works better, and is easier to wean off of", but I`d like to know a bit more!

Thanks!