Disclaimer: The following information is based on personal experience. I’m happy to answer your questions or playtest an instrument. For more qualified advice, I suggest contacting a piano tuner.
If you are just starting music, almost any keyboard is suitable – to a point. To progress further, you will eventually need the following:
This is the most important feature. The action of a piano is the mechanism that causes sound when a key is depressed, and ideally this will give a feeling of weight. Grand pianos have the best action, allowing individual keys to play rapidly and with only a slight movement. Upright pianos are somewhat less responsive.
Not all electric keyboards have a pianistic action. Some are not touch sensitive, meaning the volume (loudness) of your playing is not controlled by how hard you press. Others use a simple spring action in the style of a pipe organ. If you are looking for a keyboard with a pianistic action, look for the descriptions “hammer action” or “weighted keys” in addition to touch sensitivity.
Without a responsive, pianistic action, it is difficult to play with strength and speed. Even beginners will find it easier to develop good finger habits on a proper action.
Full size keyboard
A modern piano has 88 keys, spanning just over 7 octaves. The smaller the keyboard, the harder it is to fit some intermediate and advanced pieces into the available keys. For instance, music of the Baroque era was written for keyboards that were smaller than the modern piano. There are also larger keyboards, but these are almost never heard of.
On an acoustic piano, the damper pedal allows notes to continue sounding even after the keys are released. Grand pianos have 3 pedals: the damper pedal on the right, the sostenuto pedal in the center (a selective version of the damper pedal), and the una corda (soft) pedal on the left (lowers volume). Upright pianos use a different mechanism for the soft pedal, and may also lack the sostenuto pedal.
Electric keyboards usually have a 1/4 inch jack for connecting a pedal footswitch, but some also include a cabinet with 3 pedals like the grand piano.
Pedals, and the damper pedal especially, are important tools for expression in intermediate and advanced pieces.
Electric keyboards are cheaper and easier to maintain than acoustic pianos. Many can produce a variety of sounds (e.g. organ, bass guitar, harpsichord) and can interface with a computer via MIDI. They are also portable and can be played with headphones, making them ideal for apartments and small spaces.
Note that electric keyboards are built for different purposes. “MIDI controllers” do not produce sound on their own and are intended for digital music production. “Synthesizers” produce a diverse variety of sounds but do not have the action or keyboard size of a piano.
If you are buying an electric keyboard for use as a piano, make sure it is a good size (88 keys), has “hammer action” or “weighted keys” action, and includes the damper pedal. Reputable brands include Casio, Yamaha, Roland, and Korg.
I don’t recommend purchasing acoustic (the “real”) pianos without some research and playing experience. After playing on the pianos of various churches and schools, I find the quality of used and low end pianos is extremely inconsistent. If you do choose to buy an acoustic, stick to reputable brands (e.g. Kawaii, Boston, Yamaha) and always play test the instrument before purchase. Do your research on what to look for in the piano case, action, and soundboard – there are many books and online articles on buying a piano.
Acoustic pianos come in many sizes. The larger the piano, the longer its bass strings, which improves the piano’s sound quality. Upright pianos have vertical strings, whereas grand pianos have horizontal strings. Grand pianos are generally larger than upright pianos, have a more responsive action, and are more expensive.
Acoustic pianos are very heavy and should be moved by a dedicated moving company (look for piano movers). They also require regular tuning and other maintenance by a piano tuner, about every 6 months. If you live in Fort McMurray, there is no piano tuner in town and you will be paying significantly more for the tuners that come to town every few months.
The advantage of a well built acoustic piano is that they easily last decades if maintained, and retain their resale value. Their action and sound are also preferable to an electric keyboard, although this depends greatly on the quality of the instrument. Of course, they also look great in your living room!