Same gun all the time. The best back up to your EDC in the event your primary carry should ever go down is a duplicate of it.
Consistency is a good thing especially when it comes to a defensive firearm. Train with what you carry and carry what you train with. It's better to master one gun than be a jack of all guns but the master of none.
YMMV but it's what's worked best for me.
Before bed, Chuck Norris checks his closet for a 10mm.