The Orion Spark comes with Romer G switches which is a very new player to the game. No keycaps other than what comes stock on the keyboard are available.
The Razer on the other hand uses cherry mx compatible switches, and therefore you have more choices when it comes to replacements.
Here's a quick description of Cherry switches that I have played around with. There are other switches around such as Topre and ALPS, but that's a discussion for another time =)
Linear
Cherry MX Red
Cherry MX Black
Tactile
Cherry MX Brown
Cherry MX Clear
Tactile and Clicky
Cherry MX Blue
Cherry MX Green
Generally speaking, tactile for typing, and linear for gaming with the cherry mx browns being a good middle ground. However that is super subjective, only you can decide for yourself. The Razer switches seem to be a copy of a Cherry MX Blue from what I have experienced.