I believe STO investors have more security than ICO or IEO, as stated on one of the reply :
But as for STO, They don't just start issuing out coins, they will have to register with the required government bodies that makes they are 100% lawful. ICO is easy to launch and anyone can just do that, but STO is not like that, you will have to go through a lot of process.
The risk of being scammed in an STO is very slim unlike in ICO since it is not regulated. If ever an STO project became fraud, authority can trace all the people behind that project so there is a factor of "fear" on the side of the project developer and that factor can drive them to do better. While the unregulated ICO project developer will just do whatever they wanted to even run away with your money the instance the crowdfunding is done. So in terms of security.. STO is way more secure than ICO and even the IEO.
Check this
to learn more about STO
STO and ICO will go down. IEO is a good balance between security and accessibility.
Can you elaborate why do you think IEO is good balance of those two and how secure IEO is?