happy_wis
290
Well.... I think you know the answer already....
They are very different watches... probably only two things are similar.... their prices and they are both instruments to tell time 
Since you only post your question in the Lange forum (but not in PP forum), I bet you prefer TZ over the 5396 but you are looking for more "support" from the fellow purists for you to make such decision..... as you mentioned a word "Investment".
Personally, I won't tie the word "investment" to the Lange (at least not at this moment). I would consider Lange is just another fine watch maker available for us. You should expect to see a major drop in its value at the time when you buy it. It is similar to a new car hit the ground.
Under the current market, I would say Patek is a synonym of "investment"... you should seriously consider Patek if the importance of the investment part is significant to you.
One more think you may need to consider... I hope you understand that the new Lange is a young brand. It has less than 20 years of history (http://www.alange-soehne.com/en/origin/the_comeback.php). For me, I don't believe that "buying" a old brand name (that was out of existence for decades) and using it again means anything to me. The new Lange has to build their own history, their own tradition.
If "pass on to my son" is also a significant part in your "investment", I would suggest you to consider something with track record (and well proven) for decades. Again, Patek is king here. They can (and they will) restore any watch they made in the past... no matter how old the watch is. They can even create new part to repair their watches if the old part is not available anymore.
Of course, in the end, buying a watch is a very personal and emotional activity.... just follow your will and ignore my stupid 2-cents of comments.
Good luck