I actually have both of the iD L guide books, as when I was looking to buy one, I couldn't find any information on what the differences between the two were (so I just bought both).
In my opinion, unless for collection reasons, it's only worth getting the Mori Mori Ikusei version. The Pikapika Sodatekata version is a little smaller and seems like it's possibly more informative, but as I can't speak Japanese it's not a huge amount of help. The Mori Mori Ikusei version has a lot more explanatory images; plus, it matches the P's guide book. It's also in full colour (the Pikapika Sodatekata version has both full colour and black and white pages).
I'm happy to answer any questions you might have about the two or upload a video comparison if you'd like.