As been said around here (guitars or keyboards), one must try them out for themselves at the music stores that provide the brands and models one is curious about.
Casio, Korg, Williams and Yamaha all have good 'consumer' level models of which to choose. All provide from the 39 to 88 key deck configurations. 61 key decks (at the least to begin with) provide the 5 octave range many can use (especially those already being players) to have all the music interpretation being represented.
Williams brand is aimed at the piano player in mind (with both touch sensitive, and weighted, mechanical key models). Their models don't provide all the voice samplings (instrumental) and accompaniments (band and orchestral backgrounds) that several of the other models do.
Besides the 'higher end' models (digital keyboard pianos) that will offer up weighted keys, full 88's and even pedal effects, there are a few other 'professional standard' brands to look for and try out as examples. But, many of these will have to have the aid of added pre-amping and monitor systems (powered speakers) to get all the feature out of these units as they were meant to perform. This can get expensive if not being all that portable for set ups.
Korg gets into the digital piano as well as in comparison to Williams. There are as well, Rhodes, Roland and Kurzweil that are usually meant for stage and studio recording applications. Finding thes and you will begin to understand their particular applications if not being that practical for the average piano player. (Too bad there aren't any good Wurlitzers around in their electronic line.)
So, it will be an adventure of itself, if you can make it that, just to shop around and compare for what you will decide upon your own specific needs and appreciations as a player.
Be it acoustic (uprights, spinets or grands) or digital keyboards, it will also depend upon where you are going to have your instrument placed while you play, in having what you expect it to sound like.
Realize, the big differences in sound clarity and volume impacts if you haven't by now.