At the time I was experimenting with Studio One, it lacked a number of essential features, the most glaring being the inability to freeze tracks. It also lacked track folders, IIRC. Those limitations are now gone, though. Mostly I didn't like that I couldn't have separate MIDI and audio tracks for software instruments, and multi-output instruments were klunky. I missed instrument definition files for my external synths, and never found an event list type screen for detailed MIDI data editing. I'm not sure if version 1 had PDC, it may not have. I didn't care for the PRV, which seemed to assume you want every note quantized and of fixed duration.
This was before they added Melodyne, so that wasn't a factor at the time. But then I've had full Melodyne for years so it's still not a major selling point for either Studio One or SONAR X3.
I'm sure if I'd stuck it out and molded my brain to the Presonus way of thinking it's quite possible I'd be a happy S1 user today. They've certainly made great strides since then.
However, any time I look at other DAWs I remind myself that SONAR 8.5 literally does
everything I need a DAW to do. It lacks no essential features. Most important, I know it so well that I never have to think about the DAW itself, which is how it should be.