I think, to be honest, the more modest a player you are, the MORE important tweaking tools are, not less. If you are limited to simple chords and simple single note melody lines, use the same great style twice, you will end up sounding very similar, even on a different tune. But learn to tweak the style, only change the drumkit and bass to a different kit even, and you end up with something that sounds quite different, with a modicum of work...

Learn to write in your own OTS settings and Registrations, and you can quickly change lead sounds, and make the most of the little you ARE playing, also. It's often strange that many people won't mess much with these, going 'I'm not a great player', but in truth, they are your best friend...

So, I guess I'd say that what makes a keyboard a 'good one' is more to do with the ease that you can transform it into something new and fresh, possibly more than almost any other point. Great players can make rubbish keyboards sound great. They can make you forget about bad sounds, samples and styles, even (if they play enough to cover them up!), but more modest players need VARIETY..