I have done both.
They are both fantastic Lenormand courses packed full of information.
With the Treppner you get lots of Word file explain the card meanings, the different combinations and different spreads - including the Grand Tableau. It is very comprehensive and you can work through it at your own pace. It is based on sound knowledge and is easy and clear to understand.
I really enjoyed the Lenormand 101 because it involves screenshots, videos etc and felt more interactive. That is partly because I find I learn best by seeing something demonstrated. The expectation is that you can allow your intuition to flow a bit more when it comes to combinations once you have the basic meanings sorted. Be warned there are different meanings for some cards between the two systems. I find that I can relate to some of Melissa's meanings for certain cards and the Treppner for others. The Grand Tableau section is wonderful!
Both courses have a preference for the 9 x 4 layout and spend more time explaining that method for the GT. If you have a strong preference for the 8 x 4 + 4, you may need to adjust the advice slightly.
If you can afford to do both, it is worth it as it all helps to add to the Lenormand understanding. Good luck!