There are lots of facilities out there today. I think more and more of them are gaining on an even playing field with each other and are delivering very similar services. They are becoming commoditized in a similar fashion and it is becoming more an issue of just a cost comparison for similar levels of capabilities between sites. You should keep in mind your requirements while running in an extended outage and the ability of your personnel when it comes to remote management of the failover facility.
Beyond this, also consider what service-level agreements (SLAs) you currently have that need to be preserved while operating in a failover state and whether a backup facility can meet those SLAs. Quite often when we're assessing a disaster recovery (DR) facility, we get myopic and think specifically of disaster-type SLAs.
We often neglect the operational SLAs we have in place internally and don't carry those over to the DR infrastructure when they may be crucial to continuing business as normal. It doesn't do you any good to maintain uptime and operations if your performance may still deteriorate to the point that you lose customers or sacrifice revenue.