Speaking just for myself, I would lean toward using Aeotec micros instead of Fibaro for now.
Smartthings is in a process of transition: new platform, new app, new hardware companies. And they now expect the individual device manufacturers to maintain the integrations and “device type handlers“ that allow their devices to communicate with the smartthings platform.
Fibaro has shown little or no interest in taking over ownership of the integrations, And some of their devices which used to work just fine with the smartthings classic platform aren’t working well with the new stuff.
On the other hand, Aeotec has gone the other way, and is now the named partner for hardware for smartthings in both the EU and North America. And the UK. So just as an example, future hubs purchased in the UK will have the aeotec logo, not the smartthings logo.
All of which is to say I’m pretty sure that Aeotec will be highly motivated to keep their devices working with smartthings in the future. Fibaro, not so much. 
Both brands are good and both of their micros are good devices, this is just an organisational decision, but I think it may have an impact on individual customers.
Just my own feeling, others may feel differently, and there are certainly a lot of smartthings customers who already have Fibaro devices.