aviya
926
Welcome to our forum, WatchFan1.
Wonderful that you have the opportunity to consider an 1815 Chronograph - a beautiful watch in any generation of it.
The groundbreaking L951 movement is, of course, a key attraction. As others here have already said, Lange have upgraded it over time - both in major ways (longer power reserve, in-house balance spring and a variable inertia balance - all on the 2nd gen.) and also in more subtle ways (adopting the Datograph baseplate and re-working the reset mechanism - each on later third gen. pieces from about case no. 245xxx onwards). Regardless of the exact variant, the L951 stands up to any scrutiny and - if you own one - you will be looping it for hours: it never gets old.
On the front side, more subjective of course but in my view, the first gen is the most quirky and interesting - it's somehow got more unique character. The third gen., which I have until recently owned, is my personal favourite - opinions varied but I hugely welcomed the return of the pulseometer scale, plus all the other refinements front and back: it feels like "peak 1815 Chrono" to me. And meanwhile the second gen. left me somewhat cold, though I still see some photos of it online and really like it at first glance - then my eye quickly progresses to seeing it for what it's "missing": the pulseometer scale.
However: you said in your post you favoured the 2nd gen. so the best advice - which I'm sure you've given to many others too - is to always go for the one that smiles back at you. The pedigree and core elements are present in every generation - but only you can choose one that truly delights your technical, visual and emotional sensibilities.
I wish you well with your choice - please post a wrist shot here in due course.