The OP also asked about a difference between distros (DIY) and "something else" - and I do think that there is a large difference in the security + maintenance surface area that you have to contend with on a Platform As A Service like Heroku versus your own box.
What's more I think you hit on exactly the reasons why: I'm much more likely to screw something up by misconfiguration or lack of attention than a team of security and maintenance people at a company whose sole job is to make sure that I don't get burnt by these things.
OP is trying to get a SAAS off the ground and not (presumably) doing something with handling distro security and server maintenance - for the minimal cost difference in getting started it's hard to see how the time+effort difference in being your own sysadmin is worth it.
What's more I think you hit on exactly the reasons why: I'm much more likely to screw something up by misconfiguration or lack of attention than a team of security and maintenance people at a company whose sole job is to make sure that I don't get burnt by these things.
OP is trying to get a SAAS off the ground and not (presumably) doing something with handling distro security and server maintenance - for the minimal cost difference in getting started it's hard to see how the time+effort difference in being your own sysadmin is worth it.