Ignoring the custom setup you described (as we're changing multiple variables)... Belts versus Chains, selection...
Chains have 0 elasticity - this is particularly useful in a jam (say a component seizes or provides too much resistance). In that sort of condition, a belt will slip (and make a terrible noise), a chain will break and throw.
Belts are typically made of some form of rubber, plastic, composite, etc. - which have nice damping properties - they will create less noise at higher rpm....
Chains require maintenance when exposed to the elements - less so in a sealed/oiled environment.
A properly designed gear and chain setup with proper lubrication will last for a freaking long time without maintenance (Example is the Saturn DOHC motors in the S series' timing chain - as long as it didn't run out of oil, it would last longer than the car)
Belts are super cheap and fairly easy to replace and tension.
Chains do not tolerate misalignment - belts have a high tolerance and some can self align with the proper pulley (belts always look for a high spot to ride).
Modern belts have a fairly high power transmission efficiency (mid 90's% and up).
Modern chain is in the mid-high 90's% too (bike chain efficiency:
Headlines@Hopkins: Johns Hopkins University News Releases) but, they might be at tensioned fairly tight.
Switching from belt to chain probably won't yield any easily measurable gain in drive train efficiency.
I won't argue that one is necessarily safer than the other as a friend of mine lost part of his finger due to a belt related accident.