You can sync call logs between iPhones and iPads with "PhoneLog for iPhone & iPad" and Macs with "PhoneLog Pro", or any combination of the two.
If you are syncing between a combination of Macs, iPhones and iPads, then you may use Dropbox to sync. If you are syncing between only Macs, then you can instead choose to sync using a shared folder such as a network mounted drive. This option is not available in the iPhone or iPad version of PhoneLog.
Syncing using Apple's iCloud is not supported at this time, but is a possible future enhancement. Please send a feedback email if you are keen to see this capability implemented.