It's a more complex question than it first seems. "What do you require in a keyboard?"

I guess the simple answer would be 'Everything!'

The trouble starts when you don't realize that you could need your keyboard to do several completely contradictory tasks. For live, solo stuff, you need one thing. For studio work and pro production, you need another. For dance production, something else, for retro acts and recording, something else again.

Live, you need the ultimate ease of use even perhaps at the cost of the quality of the sounds (an awful lot of detail gets lost in a band or busy solo situation). You need an OS geared towards instant recall of any setup, seamless changes from one setup to another, conveniences like lyric readers, songbook lists, easy patch selection and fast on the fly mixing of setups you create on the spot.

In the studio, there's more time. More detail in editing voices, setups, effects, routings, etc. are required. 'Close enough' isn't a phrase that should used much! Versatility, flexibility, customizability, a degree of 'openness' even if it is just a sampler or loop player, and a VERY comprehensive set of controls make for a powerful studio tool. But they are the very things that work against you if you play out live, unless you do a highly choreographed show that never asks you to do something you haven't already prepared for.

Then there's the 'open' keyboard issue... Most people know my opinion of those... if you aren't at the top of your game, you are setting yourself up for a frustrating time getting as good an overall sound and degree of usefulness as a closed one. Whether studio OR live, but especially live...

Retro keyboards, the accuracy of the emulation is the main criterion, followed by ease of live use, again.

All different keyboards, with different focus. Expecting any one to cover everything with the same ease is unrealistic. This is possibly one of my issues with open keyboard supporters. Yes, theoretically, one good open keyboard OUGHT to be able to do it all. Sadly, IMO, they haven't made one yet that does. No doubt eventually, it can be done. But until then...

I like specialists. Got great WS's and a decent VSTi rig for studio, got a great live keyboard for live. There's a certain amount of crossover (mainly towards studio use) but each are better at one thing than the other. And I'm happy with that. Maybe, a ways in the future, someone is going to make something that IS the master of all trades, but so far, I haven't found it..!