I see what you did there, dude, you thought you would get two for the price of one, yeah?
Okay I'll bite.
MIDI keyboards (or controllers, as they're sometimes called) can be just as complex as audio interfaces. But I'm not going to lay it down completely for you. Do a quick google search for how does a MIDI keyboard work to find some information about every feature they may have.
I can however give you a couple brands that are revered by 99% of the people in small home studios.
They are M-Audio, Novation and AKAI Professional. Anything from them will be great quality, and will feature Logic Pro X and Mavericks compatibility.
Which midi keyboard do you suggest? 49 or 61 key preferred that works well with Logic Pro X please.
What are you going to play on this? Do you want piano action or synth action keys.
The feel of the keys and the quality of the action are, I think, the number one thing to look at. But what is "best" depends on why you are doing. Pianos are very different from organs. What is it you want?
What kind of keyboard instruments have you played in the past?
Just a basic yamaha keyboard loooooong time ago. Mainly using it for midi controls. Not really a great piano player. Just using the piano for basic layering.
Pianos have weighted hammer actions that transfer force into motion. Asynth action keyboard has light springs under the keys and may or may not have velocity sensitive keys. Velocity sensitivity allows you to play louder are softer.
Allpianos are velocity sensitive but keyboards can be either way. Pipe organs are not velocity sensitive and some synths aren't
Yo just have to finger out what you want. I use a piano action keyboard from Yamaha. They don't really have hammer, it's simulated with a weight in a stick but is still much different from the spring action types
You may have a local music shop, where you can try some of those, or at least look at them. Sometimes you also find folks at shops that have some experience, or even the same interest in audio that you have You can get some good opinions, and use that as a guide for what you eventually get.M-Audio, Novation and AKAI Professional. Anything from them will be great quality, and will feature Logic Pro X and Mavericks compatibility.