Well really depend of what you are looking for!
If you search for information regarding the biotope feeding and care Datz is better... and most pictures are the original L number...
downside: Only one specimen is shown can be tough for an id... no LDA number: normal it was created by the conquerence "DAS AQUARIUM"...
For id Aqualog is a bit better due that it show several specimens of each L or LDa when possible... they usually show the pattern and color variation within a Species...
Downside: basically no information about care feeding and breeding...sometimes the little informations are partially uncorrect...or really different form DATZ.
The price can also be a factor... 25€ compare to 70-80€ ...
Thanks a lot Yann ! I will go for Datz. If I need to see more Pictures I will check the Net. I think its easier to find Pictures than Bio Data in the Net.
Good to read from You !.