That's not exactly a question that has a straight answer.

In general “closed keyboard terms” I'd take the keyboard without the arranger function because it will be more advanced and totally reprogrammable, as well as designed for a much more advanced user than the one with the arranger functions.

This is the typical difference between all Arranger and Workstations keyboards right now and the type of user they are designed for. Workstations are simply designed for more advanced users who expect to have to program everything and write songs track by track.

However if it's a OPEN keyboard then the question is actually rather pointless since they keyboard technically has no function other than to be a HOST for whatever the end users needs are.

The only thing that still follows through though is the ability of the end user.

So with that in mind, an open keyboard is not ideal for the general arranger user because they can't program and are not generally technically minded. Where on the other hand the workstation & DAW users will take to an OPEN keyboard like a Duck to Water. It's simply an natural progression for them.

Obviously you Magica Alfa are not the typical Arranger user and you are one of the few who are technically minded.

Just my 2 cent's.

Regards
James