The Symbicort is a combo of Pulmicort and Foradil, not Flovent and Serevent
(salmeterol) (which is Advair) -

I haven't used this particular inhaler, but I have used some powder
inhalers in the past.  I think there are pros and cons.  I found the
ventolin diskhaler uncomfortable to use - just too much powder, which
seemed to clog in my mouth and windpipe - although some of these effects may
have been more my imagintion than real.  I guess I was using it quite
frequently too.  I also used an astra turbohaler (I think the drug was tilade)
which had a moulded fluid-dynamic turbulence mixer which was quite reasonable
to use, the amount of powder was very small (probably less than one tenth that
of the ventolin diskus) and I couldn't tell I'd inhaled much of
anything, maybe that's similar to the turbuhaler you're using.

I think there may be some advantages to a low volume powder inhaler like this -
no hydrocarbon propellant.  There are probably other advantages to powder -
greater dose per inhalation is possible since MDI's are limited
by the solubility of the drug in the propellant, and powder inhalers are
probably cheaper to manufacture (and no ozone layer damage).

Another area to consider is efficiency of drug delivery to the lungs
against how much is deposited in the stomach; some of the limitations
of MDI's in this respect are overcome by use of spacers, but you won't
need a spacer with your powder inhaler since there's no high-velocity
propellant.  All in all if the drug is delivered to your lungs
efficiently it shoud be equivalent to MDI and have a similar safety
profile, and some other advantages as I mentioned above.

-- gumbo