Hi, I am an Certified OKI Tech. Personally, I would not think that these two are compatible, simply compare the cost, you get what you pay for works here and pretty much everywhere else. X C75 is a beast, while OKIs are really nice, reliable and innovative they hold their niche but not as productive as Xeroxes C75 unit. Well, lets compare:
Finishing Options X yes, O no but I am sure OKI will come up with some should these printer prove to be a success.
White / Clear toner X no, O yes - which is an awesome option, if this is what you need - no point to compare, go get one.
LED exposure arrays are just fine, so you know - after buying OKI's engines for Phaser 7400, Xerox/Fuji built their printers using the same technology - Xerox Phaser 7500 and 7800 are LED based and most likely for 1000 lasers went bad there is may be One LED unit and that is a BIG MAY BE. I dealt with OKis for last 5-6 years, can hardly remember changing LED more than once or twice also - if it gets dirty - wipe it and you done, if toner/dust gets inside of laser unit - good luck with that.
Service contract available with toner included X-yes, O not that heard of, may be they will change the politics with this one... since you'd be buying it new, it would be appropriate to talk to your sales rep - I promise you, they won't/can't force you to buy the unit just because you called and asked few questions, same goes if you will request few samples too.
If you wind up buying one, please reply with how do you like it.
Keep in mind that model is new, the whole engine is new and raw, double check about the "lemon" policy - how does it work if you'd have to get it exchanged or returned in case it won't perform as promised, better yet get that in writing so it won't be just a sales speech. If there will be a warranty extension offered/available - take it, once again - it is new/raw engine...
Good luck