Quote from NetTecture:
Well, lets start from the back end. Zen-Fire? ZERO to Rithmic. It is a marketing label for one of the Rithmic services. A "distinguishing item" that at the end is just a new name for old shoes - NinjaTrader loves those, for example their Kinetick data service is a resold IqFeed, IIRC.
Rithmic?
High speed / High Performance trading. They advertize extremely low processing time. Naturally this is totally useless (and i mean totally) if you manually trade or trade over the internet (a difference of half a millisecond is not really relevant when you start with 20ms or more, and or have a 200ms or more reaction time), but if you get automated trading it may make a difference.
On top of that, Rithmic has some really good reputation for reliability. They also have a good clean API (compared to for example TT Fix which - ah - has issue remembering what positions you have open, no joke - they reset that every night, so if you keep overnight next day it says "0").
I am not sure I would call Rithmic "expensive" - a lot depends on how you use them. Manual Trading, Trading from home - expensive, as any gain you get is pretty much surreal compared your reaction times. COULD still be worth it, but then from other dimensions (clean API etc.), not sure performance. Colocate - it may well be a difference worth paying for just from the speed point view. They offer a tick to trade latency of 250µs.