I have to add a little caveat here. Everyone seems to be hypnotized by IGH HUBS with belt drive.
IMHO for single speed, fixed gear, or IGH a belt drive has a couple of advantages vs a chain: lighter, quieter, no grease.
The chain drive system on the other had has some real and substantial advantages over a belt on singlespeed and IGH setups.
First, you can buy several good quality chains for the price of a belt.
Second, you can change gear ratios at your leisure by changing the chainwheel and/or cog and adjusting chain length.
Third, a modern chain that is not being subjected to the abuse of a derailleur will last many thousands of miles with minimal maintenence. My 2 IGH bikes both have over 5k miles on the current chain with no end in sight. My old singlespeed went almost 12 K miles before the chain was due for retirement. And in all those miles, I have never broken a chain.
Lastly, when you are riding out in the middle of the nowhere and you have a belt issue, good luck at the local wide-spot-in-the-road bikeshop!