Pro's of coasting in neutral:
- no pumping losses from the cylinders pushing air through ("engine braking" on normal cars)
- less friction overall
- further overall coasting range for given slope/terrain

Pro's of coasting in gear:
- fuel injectors are shut off- ZERO fuel being used as long as rpms > idle speed
- full lubrication to tranny
- more regen for use later on

Con's of coasting in neutral:
- not full lubrication in some cases
- engine consuming fuel at idle rate
- forgetful drivers might forget to place back into D in a hurry
- no regen, if it matters

Con's of coasting in gear:
- engine braking (PLUS regen in hybrids) reduces coasting range significantly

In my case (HAH) I can normally get better overall FE by coasting in gear instead of neutral, since pumping losses only affect 3 of the 6 cylinders- the other 3 are sealed at low-load and normal speeds. Plus, in neutral, all 6 of my cylinders are banging away at idle consumption. On balance, my overall consumption is often lower while staying in gear, despite the shortened coast distance.

This may or may not hold similarly true for the HCH-I. It comes down to what uses less fuel for your particular model: zero used for some distance (but some used for the remaining distance), or a little used the whole way for that entire distance. The optimum configuration slides from one to the other depending on the ratios of fuel used and distance coasted- different for each model. In calculus it would be referred to as a max/min optimization problem.

I spent several months neutral coasting before switching to in-gear coasting. My FE took a noticeable jump up when I went to in-gear back in the winter.

My recommendation:
find representative stretches and see what your 'segment' FE for that stretch is both in neutral and gear. The preferred configuration may be different for different grades and even road surfaces on flat terrain! This way its not a guess. You know for sure.