on demand w/h or indirect???

RMA

hey,
have a freind with a converted contemporary into a victorian.
(a little imagination here)
all electric heat at first, but about 8 years ago had a telydine lars h/w boiler installed with a bradford white indirect for domestic h/w, and 3 or 4 circuits of radiant on first floor.
the boiler is crapping out and the Co. who installed it does not service it any longer.
This is the question,
to go with a rinnai ondemand w/h (The family is away on weekends alot) and a buderus G142 for the radiant zone, with added zones for second floor bedrooms (replacing electric bb)
or

the g142 wiith a new super store.

which system would provide the most efficiency?

thanks for your opinion
rick