Pa1X sounds more like Yamaha Tyros, less than SD-1. All 3 are very good.

I was working with it, navigation is like Triton, but has better "natural" presets.

"Songbook" option is good try, but poor implemented: it offers you arrangement to famous hit song, but sounds don't match to original.

Some arrangements sound very realistic.

I like more my X4, it's very easy and simple.