Expecting ANY keyboard (short of Wersi or MS with a full computer sequencer on board) to have the ease of a dedicated sequencing program is unrealistic. First of all, there's the completely graphical way of manipulating data. This obviously depends on the display. I certainly wouldn't want to run Cubase on a 4 inch screen!

Then there is the enormously greater choices of editing tools. By the time an arranger has developed a sequencer that powerful, it would be unaffordable...!

I agree that Roland arrangers have the best SMF tweaking tools (called Makeup Tools) but these are primarily header and global edits. Often all you need, but if you need to edit the track data directly, as easy as Roland make it (their sequencer is pretty good) it is still a pale shadow of Cubase.

I am just glad that USB makes data transfer so much easier than it used to be. Bang the sequence to the computer, edit the SMF there, bang it back to the arranger. Simple, fast, powerful.

Why would anyone need more?