I haven't given Atom a good chance since the beginning of the year, but startup was noticeably slower for me. I often use it to read/modify extremely large JSON files (tens of thousands of lines) and Atom struggled to render that. I also frequently have dozens of tabs open and Atom seemed to slow down with that many open. I've had 50+ open in Sublime before with no issue.
All that said, Sublime is not my daily driver. I use JetBrains products for that. I mostly use it to jot down notes that will eventually be transferred somewhere more permanent, temp access tokens for APIs, small snippets, JSON files, Mardown files, etc. If my main use with ST3 wasn't frequently opening and closing it, relying on its great performance when opened with my actual IDE(s), and abusing its second-to-none ability to keep files saved without actually saving them to disk, I may feel differently.
All that said, Sublime is not my daily driver. I use JetBrains products for that. I mostly use it to jot down notes that will eventually be transferred somewhere more permanent, temp access tokens for APIs, small snippets, JSON files, Mardown files, etc. If my main use with ST3 wasn't frequently opening and closing it, relying on its great performance when opened with my actual IDE(s), and abusing its second-to-none ability to keep files saved without actually saving them to disk, I may feel differently.