I wrote an article a couple of years ago comparing the
relative advantages of both these types of biomass.

I stated that wood chip had 3,500 KW/TONNE and wood
pellets had 4,900 KW/TONNE.

We now have accurate information  from consumers on the actual heat obtained
from the fuel which takes account of boiler efficiencies:

Wood pellets: 4,100 to 4,500 Kw/tonne depending on quality
of pellets.

Wood chip: Maximum 2,800 Kw/tonne. Outputs can be much
lower depending on chip quality.

Another fact is that dual fuel boilers would appear to
less efficient when burning pellets than dedicated pellet boilers. I find this
a surprising fact and could be due to boilers now being set up properly for
pellets. If you have changed from chip to pellets check that your boiler has
been adjusted for same.