I used to have logtenpro.
I can not recommend. At one point sync between iPad and iPhone was not possible, and afterwards my departure/landing time was missing. Block hours still there. When writing to the support, the answer was, it is a known glitch and we informed everybody not so sync... Ok, but I got more important stuff to do than checking emails for possible glitches on my logbook.
If you want to have an electronic logbook, my advice is DO NOT go for a LogBook app, unless they store it in a way, that you still have access to it in case the company goes bust.
Keep in mind, there is a limited amount of users, one off payment will not work out. It has to be a subscription, whatever they promise you.
Does not affect me really, luckily can download my logbook files whenever it suits me from the company website.
Cheers