Why use RDS over EC2 for Postgres? I have a database currently running on EC2. As I have to move it to a bigger machine the question of using RDS came up.

Pricing:

I can get an EC2 c3.large instance with two SSDs (16GB each), two vCPUs and 4GB of memory on demand for $0.132 per hour [1].

The closest (considering price) RDS machine would be db.m3.medium for $0.125 per hour (Single-AZ) [2]. This machine has the same amount of memory but only one vCPU [3]. Additionally I would have to pay for storage and io [2].

So the prices would be very similar for these two.

The advantages for EC2:


As mentioned already, one more vCPU.
I can put the Write-Ahead-Log on the second disc when using EC2 (great performance improvement when writing a lot to the db).
I can run pgbouncer on my EC2 instance (more performance because I can keep connections open).
I can edit the configuration file (will eventually improve performance)


The advantages for RDS:


Automatically does daily backups.


Can RDS cover the advantages that EC2 has (especially 2.)? Is there any other advantages?
Like most things, it's a cost vs effort/complexity trade-off.

RDS is easier, but less flexible, and costs more for the same level of performance.

(In particular, note that there's no way to replicate into or out of RDS)