Hi, I've used both aomei backupper and macrium reflect free. Aomei for several years on win7 and macrium for the last 7 months on win10. I've used them both for backup and more importantly for system restore.
In my experience both are very reliable. I'd say aomei is easier to learn as the UI is very simple but I found macrium more versatile and faster. One additional benefit for me is macrium gives differential backups so making backups very fast. Aomei only gives you this feature with pro (look out for the mt give aways).
With macrium, I can restore my win10 system (~40gb) in under 3 minutes.
Also macrium has some cool features when it comes to bitlocked partitions.
In summary, both are great but for a beginner I would go with aomei and for more advanced features and speed I would choose macrium.