From what I understand, the standards for 5G haven't even been finalized yet so a meaningful comparison to 4G isn't really possible. That said, there are some characteristics that are fairly certain.
5G is being touted as a different infrastructure model that depends on small cell networks. This means that instead of large cell phone towers, there could be small stations spread throughout an area on rooftops and utility poles. In cities, this could be quite beneficial and make a network easy to build out and improve coverage. In a rural area....well, we will see.
The other theoretical advantages of 5G are faster data speeds (as you mentioned) and greater capacity. This may be achievable with existing wireless spectrum, but it may not. There are a lot of uncertainties because this is still not a finalized evolution to existing standards.
As for when it will be available, that's also a bit speculative. 2020 is the year I've seen most often, but Verizon and AT&T may start limited deployment in the US as soon as 2018.