ljdawson and rmayayo did great work on their apps, and I purchased both of their apps.
Making software is not easy. I’m a software developer, too. I’m very happy that there is a paid version without ads, I definitely wouldn’t use them if I had to use the version with ads.
In my experience, they both provide superior experiences that are both familiar to people and well integrated into Android, especially Sync. Boost has more features however.
If you’re looking for a FOSS app, Connect is the next best thing IMO.