There are a lot of good songs that can be made with little or no editing, but... good luck if you wanted, for example to change meters a few times, and deep edit patterns in a hardware keyboard's sequencer.

Think of it in terms of tools.. A hammer is a great tool, but not every situation calls for a hammer. There are tools made in recent times that make it a lot easier on the body, but hey, if ya wanna wear out your arm and joints, you can still frame an entire house with a 22 oz Estwing.

I can do a lot in real time on my Tyros 2 sequencer, but there are a lot of things, especially when they start getting very complex, that I can do a lot easier in software. Yes, you can work in the arranger sequencers, but I often prefer to use a similar workflow to what you described initially, and based on my experiences with arranger sequencers, I have my doubts that you'll like the workflow aspect. It can be done, but....

This is a great forum bot, but there isn't a whole lot said here about a lot of the modern genres, and to be quite frank, not many arrangers come with an abundance of styles that lend themselves well to it. To put it another way, I have the Motif ES, which has a much deeper and more detailed sequencing package vs the Yamaha arrangers, and yet it still lags in a lot of areas to even the most inexpensive dedicated software sequencers, and although I'm not all that familiar with it, I bet your MMT-8 would be a step up from it too.

AJ