I chose the Log.
Of course you should take in consideration the size of your tank.
The log gives them a hiding place AND a resting place near the surface which all my boys enjoy.
The only fault I found with the log is that is the paint flakes off. I've never had the problem that the flakes fall into the tank because I rinse off the log during water chages and scrub it a little. It is then when I notice the paint peeling.
The Hammoks are small and have a metal wire inside that can get rust. Those harmful chemicals will leak into your water... not good. Some people remove the wire or cover the connection of the suction cup and the leaf with aquarium sealant.
Log. I had the Betta hammock and it rusted and whenever I added a medication to the tank it turned the suction cup a different color. Plus, a Betta can tear its fins, although I heard the log can do the same
I have both in separate tanks. My biiiig boy has the log (I didn't think the hammock suction cup would work in a bowl) and he can't fit inside of it comfortably because of his fins. He likes to hide underneath it though. My little boy has the hammock. He doesn't pay much mind to it, but I found him resting on it once.
Sally, I will always love you. You were my babygirl and the gateway to my bettabug. Thank you.