The Kings Rd track is considered "harder" - I've never been up the O'Neils Rd track so I've no idea how it compares, but the KIngs Rd track is definitely a lot of fun.
The Kentish Visitor Information Centre has this to say
The first track, the Mt Roland via Kings Road (Face Track), starts from Kings Road, Claude Road Village off the C136. The track turns into a steep mountain climb. This track is not recommended as it is potentially dangerous, steep and awkward. Walking time takes from three to five hours return.
Not sure where the steep mountain climb is. There is a fair amount of scrambling over rocks but I wouldn't describe it as steep and awkward. Potentially dangerous? It's all relative. I wouldn't class it as such.
Now the weather is warming up, watch out for snakes.