Both grinders are commercial grade espresso grinders. There are three types of commercial grinders;
1) Light/infrequent use - restaurant or other non-coffee oriented business
2) Occasional use - small coffee shop
3) Constant use - very busy, primarily espresso drinks, coffee shop
The Cunill Tranquilo/Astra falls into the 1st category. The RR-45 into the 2nd. Both are excellent machines for home use; both have ~the same sized burrs; both should last a home user forever. New burrs are ~$50 (S&H included).
If they're in good condition I wouldn't hesitate recommending either grinder.